Based on the literature review on membership heterogeneity in cooperatives, this paper finds that the reasons for the membership heterogeneity in cooperatives are complex, and different scholars have different opinions on membership heterogeneity. Besides, the reality of the membership heterogeneity in cooperatives is existed, and with the development of cooperatives, the membership heterogeneity will become more serious. Membership heterogeneity has both positive and negative influences on cooperatives’ development. Finally, this paper discusses and forecasts the theory innovation of membership heterogeneity and farmer cooperatives.