Abstract: The paper aims to analyze a strong precipitation weather process happened in the south-central part of Shanxi Province between July 8 to 10 in 2012, the author took general observation data and the data supplied by Micaps system, and used weather diagnosis methods to analyze the effect system of the strong precipitation, high and low air flow pattern configuration and the physical mechanism which produced strong precipitation. The results showed that: strong precipitation happened between 700 hPa and 850 hPa in the warm shear line of the “herringbone” shear line; the large value centre of the low layer of convergence was corresponding to the strong precipitation. The long-time maintaining of the convergence of the low layer aqueous vapour and the divergence of aqueous vapour at the middle and high layers ensured the longer time upward movement of the vapour; the movement of high energy tongue was in accordance with the movement of 700 hPa shear line, and was also in accordance with the movement of main line.