There were three torrential rain processes during the Meiyu period of 2003 over the Changjiang-Huaihe River basin, namely, from 29 June to 1 July, from 3 to 5 July, and from 8 to 11 July, respectively. Utilizing the numerical simulation data outputted by MM5 on the torrential rain process occurring over the Hunan, Anhui and Jiangsu provinces during 8-9 July 2003, the structure of vortex, which caused the torrential rain directly, was analyzed. Analyses from the simulation results indicated that the configuration of large-scale systems was favorable for the development of the precipitation, the direct raining system was two mesoscale vortexes at the convergence centers along a shear line of the Meiyu front. The shear line consisted of the convergence of warm and moist southerly flow and the relative dry northerly flow. The southwesterly jet at lower levels contributed the strong water-vapor transport belt from the Bay of Bengal and the South China Sea to East China and the water-vapor convergence centers in Hunan, Anhui and Jiangsu provinces, which provided the sufficient water-vapor content. At the convergence centers along the shear line at lower levels, two vortexes formed or developed, and then moved northeastward along the shear line. Furthermore, the two vortexes were located at the left-forward position of the maximum zone of the jet (it is also the positive vorticity center). Near the vortexes, there was strong convergence of water vapor at lower levels, and the coupling dynamical structure of positive vorticity region and the divergence center formed, which caused strong upward motion in the lower and middle troposphere, and had the convergent water vapor at the lower level lifted to the high level, it was beneficial for the occurrence and development of heavy rainfall.