Using the WRF mesoscale numerical model, the dynamic and thermodynamic mechanisms of cold dry air intensity change on distribution and intensity of rainstorm are revealed by conducting numerical experiments on a continuous rainstorm caused by tropical depression inverted trough in Jiangsu Province during 11-13 July 2011. The conclusions drawn from this study are as follows. The enhancement of cold air in the upper troposphere leads to precipitation reduction, and the dry cold air with a certain humidity is favorable for precipitation. Enhancement of dry cold air in the middle troposphere is good for the increase of heavy rain, but the low relative humidity is not conducive to the continuation of heavy precipitation. The stronger the dry cold air in the lower troposphere, the more intensification of heavy rain. Besides, the intensity of rainstorm is not only related to the intensity of coupling dynamic configuration of convergence in the lower troposphere and divergence in the upper troposphere, but also related to its maintenance time. The enhancement of dry cold air in the middle troposphere and lower troposphere both benefit the enhancement and maintenance of configuration, corresponding to the heavy rain. Moreover, the enhancement of dry cold air in the middle troposphere contributes to the strengthening of the lower front area and precipitation. As the dry cold air in the low troposphere strengthens (weakens), the front area strengthens (weakens), corresponding to the precipitation increase (reduction) and the southeast (northwest) movement of the rainstorm center. In addition, the coupling effects of positive MPV1 at 500 hPa and negative MPV2 at 800 hPa above the rainstorm center positively enhance the rainfall. When the dry cold air in upper and middle troposphere strengthens, the extreme values of MPV1 and MPV2 both appear before the maximum precipitation. When dry cold air in the lower troposphere strengthens, the maximum MPV1 appears before the maximum precipitation, and the maximum MPV2 appears at the same time as the maximum precipitation, which respectively has leading and increasing effects on precipitation enhancement. The greater the maximum values of MPV1 and MPV2, the heavier the precipitation.