Hydrological frequency analysis is one of the essential tasks in hydrological engineering design. Conventional methods of goodness-of-fit test, including χ^2 test and Kolmogorov-Smirnov (KS) test, are used to determine the best-fit probability distribution for hydrological data. Recently, L-moment method is widely used in frequency analysis in that it is almost unbiased in parametric estimation, and L-moment-ratios diagrams have been suggested as a useful tool for selecting a best-Fit distribution among candidate ones. Using stochastic simulation, recent studies had established a new method for goodness-of-fit test by acceptance regions of several distributions, including. Normal Extreme Value Ⅰ, and Pearson Type Ⅲ distribution, on L-moment diagram. However, only few studies have so far been made at comparisons of power of tests among the new method and conventional ones. Therefore, the purpose of power of tests among the new method and conventional ones. Therefore, the purpose of this study is to compare the power of test of several goodness-of-fit tests, including χ^2 test, KS test, and a new method based on L-moment diagram. It is found that new L-moment-ratios based test is superior to other conventional ones.