Abstract: Based on numerical experiments of two heavy rainfall cases, the effects of latent heat release are studied compararively. It is found that the effects of latent heat feedback are considerably different in different heavy rainfall systems. In the heavy rainfall on June 26, 1986 ( henceforth HR 8 6), the rainfall for the control experiment was doubled than that the where latent heat was removed in numerical experiment. But in the heavy rainfall Aug. 7, 1975 (henceforth HR75), the rainfall was increased by a factor of 5 than that for the numerical experiment without lantent heat. In addition, the latent heat release had much stronger effects in the HR75 on intensity and location of upper-and-low-level jet and on upward vertical motion than that in HR86. It is demonstrated by numerical experiments that the difference of effects of latent heat in different heavy rainfall systems is due mainly to the wind speed of upper-and low-level jet and vertical Shear of wind speed. The HR86 was positioned in the environment with stronger upperlevel wind speed and vertical shear of wind speed because it was in the vicinity of the upper-level Jet. Therefore, it was difficult to accumulate the releasing latent heat and made the CISK mechanism in full acting. The environmental conditions for the HR75 were quite the reverse of that in the HR86. The numerical experiment indicates as well that the observational result that the heavy rainfall usually takeing place on the left of the low-level jet and the back-right of the upper-level Jet, is caused probably by the feedback of latent heat, at least intensified by it.