Some conclusions have drawn from the diagnosis,comparative analysis and numerical study of typhoons with varied precipitation intensities. It is found that the typhoon rainstorm is associated with the presence of a frontal zone,high- and low-level jet;an intense frontal zone is responsible for the enhancement of 200 hPa southwesterly jet and ageostrophic divergence on the rear right,whose effect will excite gravity-inertia waves;the adjustment(spanning 3～6h)is none other than the abrupt intensification of the rainstorm,giving rise to the strengthening of low level jet that carries abundant water and momentum into the rainfall area for still heavier rain;after the ending of the adjustment,precipitation is kept steady.