By use of AWS and other upper data, NCEP reanalysis, satellite and rad ar data, the reasons of heavy rain and strong wind in Shanghai caused by Typhoon Krosa (0716) during Oct. 7-8, 2007 are analyzed. Results show that the precipit ation in Shanghai can be divided into two phases: the first is strong precipitat ion caused by the mesoscale cloud evolved from the periphery of typhoon; the se cond is the steady precipitation caused by combination of cold air and typhoon. The time of cold air invasion coincides closely with that of precipitation in Sh anghai. The invasion of cold air is the main reason of heavy rain in Shanghai. I n addition to the rich water vapor of typhoon itself, the subtropical high weake ns on the northern side of typhoon and wind direction turns to southerly on th e midhigh level of troposphere, the heat and vapor are providedfor the developme nt and maintenance of strong precipitation on the periphery of typhoon. Southwar ds cold and dry air together with warm and waterish current on the periphery of typhoon lead to stronger convergence, which provides the dynamic elevation mech anism for mesoscale convective cloud on the periphery of typhoon. Due to the f limsy cold air, the warm core of typhoon on the high levels is not destroyed. It leads to the cold air hovering near Shanghai, which slows down the moving vel ocity of typhoon and helps to durative heavy rain in Shanghai.