Traditional flood frequency method mainly focuses on one gauging station. If series gauging stations located in the same region and there are some dependence among them, at-site frequency analysis method may lead to overestimating or underestimating the regional flood risk. Therefore, it is great need to apply regional flood frequency analysis instead of at -site flood frequency analysis. In this paper, we introduced trivariate asymmetric Copula function to establish the joint distribution of annual maximum flow. The multivariate return periods were calculated based on Copulas and the Kendall’s measures. Results show that the occurrence probability of T-year flood in the region is much higher than the probability of that at site.