Based on 1°×1°NCEP reanalysis data of 2008, conventional meteorological data, automatic station data, surface intensive observations and Doppler radar echo, the influences of circulation background on the track and precipitation of stron g typhoon Hagupit are synthetically analyzed, and the physical characteristi cs are also diagnostic analyzed. The results are as follows: (1) The main reason why typhoon move westnorthwest steadily is that on 500hPa level, the z onalsubtropical high on the north strengthens the east flow and rear southeast flow, and the differences between maximum east wind on the north and maximum west wind on the south increase; (2) Analysis of Doppler radar base reflectivity products show s that the convective echo in rain belt develops on the upstream sea, but quickl y weakens when it moves downstream towards to the land. The vertical integrated liquid water (VIL) is a good indicator to the estimate of precipitation both on amount and area. In the typhoon rainfall system, the different density of liquid water in cloud can make big difference in precipitation with same VIL, sometime s the difference may reach 2.5 times or more. Doppler radar product OHP (one hou r precipitation) is consistent with actual precipitation area and amount very we ll, especially with precipitation area, and OHP has a good corresponding relatio nship with both R and VIL products; (3) Physical characteristics, such as vertic al motion, vorticity and water vapor flux divergence, all are in favor of precip itation increase when “Hagupit” moves westnorthwest.