Abstract: To discuss the cause and physical mechanism of summer heavy rainstorm in Shandong Province, and provide valuable reference for the simulation and forecasting analysis of strong rainfall, the heavy rainstorm process on July 29—31 2015 in Shandong was simulated and diagnosed by the conventional observation data and WRF model. The results showed that: (1) this heavy rainstorm was caused by the interaction of eastward westerly trough and vortex, shear line in lower troposphere layer, the location and movement of weather systems showed a good agreement with rainstorm area; (2) the WRF model could simulate the weather system quite well, while the simulated location and range of rain belt were basically identical with the actual situation; (3) two sources of water vapor were discovered through analysis of water vapor flux at 850 hPa and the vertical section of water vapor flux divergence, and there were shear line and vortex on the left side of southwest jet. Strong low-level convergence cooperated with large water vapor flux, which caused strong water vapor convergence. The sustained convergence and upward movement of large water vapor provided sufficient moisture for the heavy rainstorm. This process was a typical heavy rainstorm at flood season in Shandong, the coordination between weather systems at the upper and lower troposphere together with instability conditions were very beneficial to the development of severe convective weather. The simulation results of WRF model could make up the shortage of conventional observation and reanalysis data in temporal and spatial resolution, and be helpful to analyze and understand the heavy rainfall process better.