Based on knowledge-based theory, this paper analyzes the effect of variety of knowledge base on the selection of cooperative partners by using the patent data of 51 firms in Chinese electrical electronic enterprises during 2009 to 2015. Combining the proprietor of patents, the partners are divided into two types of universities or scientific research institution and other enterprises, and the multiple logistic regressions are used to test the relationship between variety of knowledge base and the selection of cooperative partners. The results show that, with the improvement of the related variety of knowledge base, the enterprise prefers to cooperate with other enterprise and university or scientific research institution than non cooperation. With the improvement of unrelated variety of knowledge base, compared with non cooperation, the enterprises are more inclined to collaborate with other enterprises.