T-year flood estimation at a given location in mountainous areas is a crucial task for design of hydraulic and civil infrastructure facilities. One of the key steps in flood frequency analysis (FFA) is the selection of a suitable distribution. More than one distribution is often found to be adequate for FFA, and choosing the best one is often less than objective. In order to overcome this difficulty, generalized beta distribution of the second kind (GB2 distribution) was introduced in this study. And the prin ciple of maximum entropy method (POME) was employed to derive this distribution with its parameters to be estimated. The Colorado River was selected as a case study. The maximum stream flow data from the sites, Steamboat Springs, Near Colorado-Utah and Hoover Dam, were considered to test the performances of GB2 distribution. Finally, the fitting results of GB2 distribution at Hoover Dam were compared with those of common used distributions in hydrology. The results indicate that GB2 distribution is an appealing option for FFA, since it has four parameters and include some well-known distributions. Compared with the widely used distribution in hydrology, the performances of Gb2 distribution is comparable.