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As graphene has been discovered since 2004, a large amount of papers investigating the fundamental physical and chemical properties of graphene has been published. However, the applications that perfect taking advantage of graphene's properties are bare. This thesis focused on the development of graphene and graphene oxide (GO) based materials and their applications for electromagnetic ranges such as antennas, absorbers, wireless energy harvesting devices, sensors, and so on. In this thesis, physical exfoliation of graphene from graphite particles has been well discussed and compared. Both popular bath sonication and mechanical shear-mixing methods have been used and compared. The cost, concentration and conductivity of exfoliated graphene have been optimized. Moreover, the graphene based low-cost screen printing inks have been developed and discussed in this thesis. Excellent conductivity property allows engineers to produce wireless connectivity antenna operational from MHz to tens of GHz. Applications of printed, flexible Near Field Communication antenna (NFC), ultra high frequency Radio Frequency Identification (RFID) tags, wireless NFC sensors and ultra-wideband energy harvesting system have been designed, fabricated and demonstrated in this thesis. Due to the advances of ink preparation, cost and electrical properties, chemically exfoliated GO is used to replace physical exfoliated graphene on certain occasions. Printing and novel reduction process which can control reduced graphene oxide's (rGO) conductivity has been demonstrated as well. The fabricated rGO laminate not only can be used in flexible electronic circuits as conductors or resistors but also highly efficient to absorb microwave radiations with proper design. A printed Jaumann structured microwave absorber has been characterized and compared with standard absorber which is consisted by graphene loaded composites. This thesis also presents the latest microfluidic RFID sensors for stretch sensing. The liquid, high conductive alloy based conductor has excellent sensitivity and repeatability comparing with lossy, rigid graphene based materials.