This paper studied the effects of applying multi-functional water retaining agent on the yield of alfalfa. The results show that: the yields of alfalfa increase when different amount of water retaining agents are applied. The increasing rate of the yield increases with the increasing of the application rate. However, the best amount is 3 kg/mu from the point of the largest economic benefits. The application of multi-functional water retaining agent can increase the dry matter accumulation of alfalfa.