Six cloud microphysical parameterization schemes of WRF model with high resolution and multiple moisture variables are conducted to numerically simulate a squall line in the northern Jiangsu on May 16, 2012. Results show that the echo reflectance, TS scores about heavy rain, structures and strength of the mimetic squall line simulated by LIN scheme are obviously superior to the other five cloud microphysical schemes. Moreover, the variation trend characteristics of moisture variables over time in different cloud microphysical parameterization schemes were analyzed and several sensitivity experiments in allusion to LIN scheme were carried out to clarify the microphysical transform process among different moisture variables. Experimental results show that the mixing ratio of graupel or hail is the maximum in all moisture variables and is the most important part of this squall line. Rainwater, originated mainly from the melting process of graupel and hail at the middle level and partly from cloud water, is the direct source of surface rain. The primary moisture variables, namely graupels or hails, are transformed from the conversion of raindrops to graupels or hail due to rain accretion. The accretion of drop water by graupels is the secondary contribution. As for the collection and accretion processes between cloud ice and snow as well as the autoconvertion, they are considered as negligible in the graupel and hail formation.