Abstract: A heavy rain process over Jiangsu province caused by typhoon 0108(Toraji) was st udied with the aid of MM5 model. By the analyses of its height，temperature and winds field features, it was found that after typhoon landfall, the center press ure increased but its gale areas still have expending tendency, formatting stron g wind transfiguration. Due to the frontal barocline，its temperature field stru cture evolved from symmetric warm center to asymmetric half cold and half warm e xtratropical cyclone. And the winds field also has such asymmetric structure. After calculation of every items distribution of frontogenesis function, it was found that in the early stage of raining the effects of transfiguration item on frontogenesis function was earlier，larger than the others, played important role to typhoon's transition. The result of frontogenesis forced strong convergence, upward motion and geostrophic departure. Then the 0108 typhoon was reintensif ication. In the right back area of upper southwest Jet there existed obviously g eostrophic departure positive divergence, which developed and maintained heavy rainfall.