The mesoscale system characteristics of heavy rainfall in central Yunnan Province on July 21,2003 is analyzed with the MICAPS data, FY-2 satellite observatory data and the observatory data of Kunming CINRAD-3830cc. It is showed that collocation of warm advection at the 500 hPa with cold advection at the 700 hPa,trough at 500 hPa,shear line at the 700 hPa ,and cold front on the surface are the macroscale circulation background which brings on this heavy rainfall process; the favorable environment condition of developing MCS is formed in instability of high energy and high wet,heavy vertical wind shear；the characteristic of Doppler echoes showed that the developing and uniting of heavy convective storm correspond with the region and intensity of the heavy rainfall;mesoscale cyclone,mesoscal convergence line and contrary wind area, which appear in radial velocity, are the direct influence systems which bring on this heavy rainfall process.