Abstract: Based on the Focal Mechanism inversion method of using the polarities of P, SV and SH waves and their amplitude ratios (FOCMEC), combining the seismic waveform data format in China, an interactive program of FOCMEC to invert focal mechanism is developed with Delphi object-oriented language, and detailed description of the calculated principle, instructions and precautions for use in is also provided in this paper. The inversion program has been proved accurate and reliable through rigorous testing and comparison.