On 30 July 2015, a warm-sector extreme severe precipitation process broke out in a wide range of Shandong Province, and the prediction deviation was large because the triggering mechanism was not obvious and the forecasters’ judgment of the development direction of the convection system was insufficient. By using multi-source observational data, the triggering mechanism and evolution of convective system organization are analyzed in this paper. The results show that the upper trough and the low-level jet favored the occurrence and development of the deep wet convection. There was sufficient water vapor and favorable thermal condition before the convection. The horizontal convective rolls shown on the cloud and radar images indicated that the potential of convection generation and development was enhanced. The cold air intruded into northern Shandong through Bohai Sea and triggered the original convection, which further strengthened, generating the surface cold pool and the gust front. The gust front continued to trigger convection, forming a backward developing multi-cell storm. At this stage, the low-level environmental wind direction determined the development direction of convective storm. The mechanism for the organization and maintenance of the convective system is as follows: the strengthening of the surface cold pool and the development of convective storms formed a positive feedback, the surface cold pool and low-level environmental vertical wind shear reached a dynamic balance, and the multi-cell storm gradually developed into a linear mesoscale convective system (LMCS). With the gradual enhancement of the deep vertical wind shear, the structure of LMCS became closer.The mechanism of weakening and extinction of convective system is as follows: blocked by the terrain in the middle mountain area of Shandong Province, the main body of the surface cold pool remained in the central part of Shandong Province, the intensity of the gust front in the front of the cold pool decreased rapidly, and the LMCS was divided into east and west segments, then the east and west segments of the LMCS weakened and died out under the unfavorable low-level vertical wind shear. The RKW theory is applicable to explain the evolution of the LMCS organization.