The invention discloses a transformation method of input data of simulation software of a power system, which can transform an input data file with PSASP (Power System Analysis Software Package) program format into the file with PSS/E (Power System Simulator / Engineering) program format, so as to solve the problems that the PSS/E software simulation research of the power system is difficult to build a model and has large modeling capacity. The method comprises the steps of after transforming data type of bus data, load data, parallel capacitance reactor data, generator data, alternating-current line data, two-winding transformer data and three-winding transformer data with PSASP program formats, writing the data into a load flow calculation input data source file with PSS/E program format according to the bus number order; after transforming data type of the generator and regulator data with PSASP program format, writing the data into a dynamic analysis input data file with PSS/E program forma according to the PSS/E self-defined model format. The method not only enables the PSS/E software simulation modeling of the power system in our country to be possible, but also provides a quick path for preparing PSS/E simulation modeling base data for a major power grid, thus, a great amount of data input working is saved.