By means of routine sounding and intensive surface observation data, satellite c loud pictures and new generation weather radar products, a diagnosis is performe d to the heavy rainstorm process induced by typhoon Haitang inverted trough on J uly 22, 2005. The results suggest that:1) This process is generated because northward inverted trough of typhoon Haita ng combines with weak cold air in we s terly belt, which is a classical reciprocity process between mid and low latitud e weather systems. 2) Abundant heat and vapor are transported from low latitude sea by the lowlevel jet in the east of inverted trough, and the left to invert e d trough becomes the headspring of mesoscale system. 3) The intensifying highl e vel anticyclone enhances the pumping effect, which strengthens convergence of ai r and rainstorm. 4) In the satellite cloud pictures, it is seen that the direct cause of the heavy rainstorm is the genesis and evolution of conglomeration and closegrained intensive mesoβ convective system. 5) In Doppler radar ref l ectivity field a lot of mesoscale echo belts converge, which induces the echo an d rainfall increasing. 6) During rainstorm, it is obvious nonuniform in horizo n tal wind according to the Doppler radar radial velocity field, there is large sc ales intensive convergence in mid and low levels, and wind direction are discont inuous in vertical. The vertical wind shear can provide kinetic energy for the d evelopment of convective cloud, which is advantageous to large thunderstorm clou d evolution and rainstorm occurrence. The reversed wind appears in the inflow a rea many times, rotates northwards in the form of cyclonic rotation and merges w ith the positive speed area. The strong echo and rainstorm appear in the area a nd passing way of reversed wind.