The mechanism of the impact of social capital of scientific and technological intermediary on knowledge transfer is not yet clear. This research tries to build a theoretical framework of the social capital of scientific and technological intermediary for the knowledge transfer performance, and also selects the incubators of the Science and Technology Park of Nanjing University as a typical case of the scientific and technological intermediary, analyzes the differences between the social capital of scientific and technological intermediary and the social capital of the government, colleges and universities, enterprises and different subjects of knowledge innovation through open research, and discusses the effect and mechanism of knowledge transfer, so as to clarify the nature of social capital of scientific and technological intermediary, and give play to positive effect in the knowledge transfer and innovation, and provide scientific basis and reference experience.