A convective rainstorm with mesoscale characteristics occurred in northwestern Shandong province on 3 August 2015. Based on both conventional and unconventional observation data, the environmental conditions, initiation, evolution of convective systems, and rainstorm distributions are analyzed in this paper. The results show that this rainstorm event was typically induced by upper-level trough and surface cold front. Under circulations of high level divergence, middle level trough, low level shear line and LLJ, favorable environmental conditions for the rainstorm were composed by large atmospheric precipitable water, high low level specific humidity, deep wet layer and warm clouds in middle and low level, and large CAPE. Warm area convections and cold frontal convections contributed to the rainstorm jointly, while the warm area convections were generated by the surface convergence line, which located in the area of large ground dew point temperature and on the south edge of the low-level wet tongue. In Liaocheng, train effect was formed and further enforced the heavy rainstorm. After the cold front invaded into the low pressure, the cold frontal convections and the warm area convections merged into a strong convection band. The track of the convection band turned to the east gradually, together with the weakening of the train effect. A bow echo formed behind the strong convection band, generating strong winds. The rainstorm has characteristics of tropical heavy rainfall. The strong convection band is shown as a flat mesoscale system on the satellite imagery, and the region, where hourly precipitation equal or greater than 50mm, is corresponded to the area where TBB is lower than -70 ℃.