Using a variety of observational data and NCEP/NCAR 1°×1° reanalysis data, a diagnostic analysis is made of two consecutive heavy rainfall events on 30 July and 1 August 2012 in the northwestern Shandong Province. The results show that the heavy rainfall formed in the warm air around the south edge of the subtropical high in front of the steady westerly trough; a typhoon moved northward along the coast of Southeast China; the subtropical high strengthened and moved northward; which provided a synoptic background for the heavy rainfall events for two consecutive days. At the lower level blow 925 hPa, both the southeast winds from the southeast coast and the east winds from Bohai provided moisture and energy supply for the heavy rainfall, leading to higher humidity, high temperature, convective instability, and high CAPE. The first heavy rain occurred in south winds and warm air with strong intensity and short duration. During the second heavy rain, the lowlevel cold air invaded and the warm air were lifted; there was convective precipitation in the early stage and stable rainfall in the later, with weaker intensity and longer duration. The shear line with a reverse trough and mesoscale vortex circulation in 850 hPa and below were the influencing systems for the heavy rainfall events. At lower levels, the northeast air flow from the Bohai Sea and the southeast warm air from the coast of Southeast China generated a mesoscale vortex, which induced cyclonic converging ascending and triggered the release of instable convective energy. Convective cloud clusters formed a stable Mesoscale Convective System (MCS) in the northwestern Shandong, resulting in obvious train effect and backwardpropagation characteristic. The heavy rainfall had a strong diurnal variation, enhanced at night and weakened in daytime.