Abstract: Microtopography has an important impact on basin irrigation performance. Considering both stochastic characteristic and spatial correlation of the surface relative elevation, a method used to stochastic modeling microtopography distribution was based on the Monte-Carlo technique and the semi-variance approaches, and a two-dimensional surface irrigation simulation model was used to evaluate impacts of stochastic modeling microtopography distribution and its discrepancy on the basin irrigation performance. Research results show that for the same standard deviation(S_d) of surface relative elevation, the effect of discrepancy on microtopography distribution on the basin irrigation performance is dependent directly upon the size of S_d. When the S_d is no less than 3 cm, the discrepancy on microtopography distribution makes a significant impact on the basin irrigation performance, while the S_d is less than 3 cm, the effect is relatively small. It suggests that any one-set of stochastic modeling microtopography distribution under the condition of S_d<3 cm is representative of whole, which can be used as the input data of the two-dimensional surface irrigation simulation model for evaluating the impacts of microtopography distribution on the basin irrigation performance.