By using routine observational data, mesoscale observatioal data, sate llite cloud image, radar echo,T213 model products and diagnosis analysis means, the ra instorm event over Shandong province during 18-19 July, 2007 is analyzed. The we ather system, vertical stability of atmosphere, convective available ene rgy, water vapor condition and dynamically triggering mechanism were discussed. The characteristic of convective clouds was worked out. The result shows that th e rainstorm was caused by the interaction of the cold vortex over northeast Chin a, westerly trough, the southwest warm and wet airflow on the edge of subtropica l high over the west Pacific and the cold air from the north. The strong southwe st airflow set up the water vapor channels where the water vapor can flow to Sha ndong province. The forwardtilling trough and increase in the temperature and humidity in the low level atmosphere caused the intensively convective instabilit y and symmetrical instability, which provide sufficient water vapor and energy f or the rainstorm. The strong northeast winds converged with strong southwest air flow on low level atmosphere, so that the vertical vorticity increased, the conv ergence and ascending motion augmented, which trigger the instability energy rel eased, produced mesoscale convective cloud mass and heavy precipitation. Meso scale low pressure formed before the ground cold front, so the convergence and as cending motion increased more and more, which resulted in MCC and rainstorm.