In order to analyze the precipitation difference in Nantong influenced by similar track typhoons Yagi (1814) and Rumbia (1818) in Nantong, the synoptic situations are analyzed and the physical quantities such as water vapor flux, pseudo-equivalent potential temperature, moist potential vorticity (MPV) and vertical helicity are diagnosed in this paper. The main conclusions are as follows. 1) The tracks of the two typhoons are mainly affected by the subtropical high and cold air, and the air flows at the edge of the subtropical high guide the typhoons. Both typhoons follow the movement trend of divergence center at 200 hPa. 2) The intrusion of strong cold air, the slow movement in the saddle field, the strong positive vorticity and intense ascending movement, the strong water vapor transport and long-term low-layer water vapor convergence, the enhancement of atmospheric baroclinicity and the increase of wind vertical shear are all the reasons for the heavier precipitation caused by Typhoon Rumbia. 3) The heavy precipitation has a good correspondence with the increases in water vapor flux convergence, the positive vorticity center, the intense ascending movement in the lower layer, the large values of the pseudo-equivalent potential temperature in the lower layer overlapped by the upper gradient of the variables, the increase and development height of the vertical helicity.