Genetic parameters in net photosynthesis were determined by Hayman method during flowering and fruit set stages of 6 parent(Capsicam annuum L.) cultivars and their 15 cross combinations established by the (1/2) n (n-1) diallel cross. The results of regression analysis of array covariance (Wr) and array variance (Vr) indicated that the net photosynthetic rate didn’t genetically coincide with the additive-dominant model. The results of correlation analysis of Wr+Vr and parent (Yr) indicated that Wr+Vr values were larger in the parents with more dominant genes governing high net photosynthetic rate. The genetic parameters showed that the dominant effect variance was more importance than the additive one in the inheritance of net photosynthesis during the flowering and fruit set stages, and epistatic effect was found significant as well. The parents had low narrow heritability and the heterosis was less obvious at the early stages of the flowering and fruit set than the middle and late stages.