Abstract: The heavy rainfall over Hunan Province in July 1996 was studied. The main conclusions are made as follows: (1) Persistent rainstorms causing flash-flood in Hunan Province lied in the front of 500 hPa short wave troughs. (2) MCS generated and detained in the same area, which is the direct reason causing lasting heavy rainfall. (3) By warm advection in the lower troposphere and other large-scale forcing, the upper troughs maintained over the middle of the Yangtze River Basin, which brought continuous lifting movement in the rainstorm area. At the same time, continuous moisture convergence and potential instable energy transport in the lower layers provided enough water and energy for lasting heavy precipitation over the rainstorm area。