Numerical simulation of two meso-scale rainbands in a meiyu-front torrential rain process in the Jianghuai Basin on June 27, 1981, has been conducted successfully in terms of MM4.Diagnostic analysis is given of the modeling data to reveal the mesoscale structure of this weather system and the special attention is given to the two mesoscale rainbelts formation and maintenance mechanism. The feedback effect of the latent heating from cumulus convection condensation is also analysed with the dry and wet control experiments. It is found that the rainbands result from the joint effect of the development and dispersion of inertial-gravitational wave, and the coupling of upper and low jet, and cumulus convection heating feedback obviously strengthens the upper and low level jet.