A diffusion simulating system of point source catalysts in convective clouds is established based on the theory of catalyst diffusion in convective clouds，and the system design and its application are described. The relationship of catalyst diffusion to the time, wind speed, turbulence coefficient, and vertical speed is discussed. The results indicate that in convective clouds the catalysts diffuse relatively quickly and the diffusion speed can reach a steady extension after several minutes; the larger the wind speed and turbulence coefficient, the wider the diffused area can be; the catalyst diffusion is mainly concentrated around the explosive height. The conclusion could be useful for artificial precipitation enhancement in convective clouds and the evaluation of precipitation enhancement effectiveness.