The properties of a nonlinear mutualism model under stochastic perturbations are discussed along with the problem of the optimal harvesting strategy. In order to study the dynamic behaviors， the existence and uniqueness of positive solution to the model are proven by the comparison principle of stochastic equations， and the criteria for persistence in mean and extinction of two species are given. Finally， by using the aggregation and ergodic method， the explicit form of optimal harvesting policy is obtained， together with the numerical stimulation showing the growth situations of two species under exploitation， which not only help human beings take fully advantage of nature and gain maximum benefit， but maintain populations at a reasonable level， keep species from extinction， and guarantee the biodiversity.