Abstract: At present, there are few systematic software for rainstorm and flood frequency analysis and calculation. In order to resolve this problem, the software of IWHR rainstorm and flood frequency analysis based on conventional moments and L-moments was developed. The software can realize manual and automatic parameter tuning based on continuous data sequence or discontinuous data sequence, and the automatic parameter tuning includes the conventional moments and L-moments. In this paper, the software is introduced and the test of conventional moments and L-moments is compared and analyzed. The results show that the L-moments can be used to estimate the parameters more accurately and reliably than the conventional moments, and it can resolve the problem that the calculation results based on the conventional moments parameter estimation method are small, and provide scientific support and basis for engineering design and engineering scale determination.