Benefit sharing on transboundary rivers is an approach to address equitable and reasonable development and utilization of transboundary water resources (TWR). Through analyzing a few typical benefit sharing cases, this paper provides a systematic discussion of the theory of TWR benefits sharing. TWR features a kind of common pool resources (CPRs). Its benefit sharing subjects are the riparian countries. The shared benefits usually include flood prevention, power generation, navigation, irrigation, contributions to society and culture, etc. The benefit sharing modes mainly include shared benefits and responsibilities, reciprocal rights and obligations, equal benefit distribution, cost proportion-based benefit sharing, and demand-based benefit sharing. The first step in the realization process of benefit sharing is the sharing of data and information. Second is the benefit identification and evaluation. Third is the establishment of a mechanism to guarantee the benefit sharing. The conditions for realizing benefit sharing depends on, first, if the riparian countries are willing to cooperate with each other; second, whether the cooperation can bring incremental benefit or cost reduction in comparison with unilateral operation; and third, if the benefit distribution is equitable and reasonable and can stand the test of time.