A heavy rain to rainstorm event on the west of Gansu Corridor in 2011 was analyzed, using observated precipitation data, NCEP/NCAR reanalysis data and simulated results. The results show that: The cause of heavy rain was geopotential height which be high in north and low in south, and the convergence of airflow of warm and moist from south and cold air from north on the west of Gansu Corridor. So much water vapor was provided by three vapor sources for this heavy rain process. Before the rainstorm, the atmospheric energy is accumulated, then the energy began to release when heavy rain occurred, and finally to the end of the rainstorm, the energy release over. The entire layer was updraft over the precipitation area when the heavy rain occurred. The strong updraft not only made the warm and moist air convergence and uplift but also released potential heat and heated atmosphere during the ascent, then formed positive feedback and made the vertical movement enhance. The Q-vector was analyzed. It is showed that distribution of Q-vector was in accordance with the precipitation area. There was no good correlation between the intensity of the Q-vector convergence and the intensity of rainstorm, but center value of Q-vector convergence less than -3*10~(-15) hPa~(-1)·s~(-3) if only there is precipitation. So Q-vector convergence zone can be better forecast rainstorm and large rainfall districts, but not able to forecast rainstorm intensity. Finally, through numerical simulation, the actual precipitation value center was coincidence with simulated precipitation center. The movement and development of atmosphere circulation was analyzed by high space and time resolution numerical model results. Simulation of the MCAPE and radar reflectivity factor and other physic index has good instruction significance to this precipitation process.