The subject of this research is devoted to the analysis of the Lak students’ language transfer in learning and using Persian. This subject expresses the subjects under study, variables, description of the situation; that is the the descriptive analysis of the data. In this research the variables are: language transfer, Laki language as the first language (L1), Persian language as the second language (L2), learning and the use of Persian language. In the present study the researcher is looking for causes and types of language transfer from L1 into L2 and vice versa.The researcher has observed the use of Persian by educated and common Lak speakers in different situations, and has decided to investigate this subject. The general purpose of the present study is to analyze interlanguage of Lak learners in acquiring and using Persian. The researcher intends to discover the elements that these learners transfer from their L1 into the L2 in the course of making their interlanguage. Interlanguage refers to the middle phases between L1 and L2. Learner language is oral or written language that is produced by leaners. The role of interlanguage is providing data to study L2 learning. The purpose of this research is to describe and explain language learners' competence and development, and its growth over time. Competence can be analyzed only through a kind of performance. Transfer is a term used in applied linguistics to refer to a process in foreign language learning whereby learners carry over what they already know about their first language to their performance in their new language. Crosslinguistic influence (CLI) or - the influence of a person’s knowledge of one language on that person’s knowledge or use of another language - is a phenomenon that has been of interest to laypeople and scholars alike since antiquity and most likely ever since language evolved. Transfer phenomena often came to signify sloppiness, narrow-mindedness, and lack of mental clarity and sound thinking (Jarvis & Pavlenko, 2008, p. 1-2). These views were challenged in the 1940s and 1950s (Lado,1957; Fries,1940; Weinreich, 1953). Discussion of language transfer moved to a scholarly footing, legitimizing it as an unavoidable feature of language learning and use and exploring it as a linguistic, psycholinguistic, and sociolinguistic phenomenon. Since the 1950s, a number of additional books have dealt extensively with transfer, including, in chronological order, Vildomec (1963), Gass and Selinker (1983), Kellerman and Sharwood Smith (1986), Ringbom (1987), Dechert and Raupach (1989), Gass and Selinker (1992), Sjoholm (1995), Jarvis (1998), Hufeisen, and Jessner (2001, 2003), Alonso (2002), Cenoz, Hufeisen, and Jessner (2003), Cook (2003), Arabski (2006), and Ringbom (2007). Language transfer affects all linguistic subsystems including pragmatics and rhetoric, semantics, syntax, morphology, phonology, phonetics, and orthography. Research on transfer, has had a discovery nature, and researchers have tended to follow a concatenative approach. According to Jarvis and Pavlenko (2008, p. 4-8), the new era of research characterizes four features about language transfer: Jarvis and Pavlenko (2002) are among those who introduced bidirectional transfer. In the oral and written production of a user of L2, crosslinguistic influence can function in both directions simoltaniously, from L1 to L2 and from L2 to L1. Bidirectionality refers to a two-way interaction between two linguistic systems of an L2 user. Bidirectional transfer enjoys a multicompetence framework that is a specific speaker-hearer with a unique linguistic system. Within this framework bidirectional crosslinguistic can be discussed and understood as a complex process which may affect not only additionally learned languages but also L1 competence. Conceptual transfercan be characterized as the hypothesis that certain instances of crosslinguistic influence in a person’s use of one language originate from the conceptual knowledge and patterns of thought that the person has acquired as a speaker of another language. Different researchers consider different causes for language transfer. Researchers like Corder (1983) are trying to explain transfer on the basis of communication. From this view point, transfer is either a performative phenomenon or a product of it. Ringbom (1992) also claimed that there is a relationship between transfer and learning. Transfer can occur as a result of differences and similarities between two languages. Major and Kim (1996) showed that Korean English learners lerned /z/ sound better than the similar sound /ʤ/.Some others believe that transfer works along with other causes. Sociolinguistics, markedness, prototypes, language distance, and factors of language development affect language transfer. In their revised position on transfer, Gass and Selinker (1993) state that it is not incompatible to think of L2 acquisition as being affected by two interrelated processes: first, the learner's build-up of a body of knowledge in which he or she tests hypotheses formed on the basis of the available L2 data and second, the learner's utilization of the knowledge of L1 and other languages known to him or her (Johnson & Johnson, 1999, p. 355). Learners, consciously or not, do not look for differences; they look for similarities wherever they can find them. In their search for ways of facilitating their learning task, they make use of intralingual similarities, which are perceived from what they have already learned of the TL. Ringbom, (2007, p. 10) has shown that Swedish speakers learn many aspects of English vaster than those of Finish learners of English. He attributes these differences to the fact that Swedish and English are typologically closer. Speakers of Roman and Germanic languages have better understanding of English vocabulary than speakers of non-Indo-European languages.