Abstract: For the factors like socioeconomic development and climate, regional water requirement is random. In view of the fact that Copula function can be used to describe the autocorrelation of event series, stochastic simulation model of regional water requirement is established based on Copula function. This model could reflect the correlation between monthly water requirements, and overcome the disadvantage caused by the simulation of monthly water requirement independently. Taking the middle-lower reaches of Han River as study area, the availability of the proposed model is verified by the comparison between the results of the model and those of Cholesky model. Results suggested that the proposed model can preserve the statistical properties of the calculated data series, especially the skewness coefficient and correlation coefficient, and provide a new way for regional water requirement simulation.