The present paper is devoted to the causes of local severe rainstorm produced by Typhoon No.8807.They are 1)abundant water carried by the storm;2)highly unstable energy for and triggering to the rainfall offered by the low-level meso frontal zone in relation to the spiral-form cloud/rainfall sector of the typhoon and inhomogeneous solar radiation;3)local topography and frictional factors responsible for the fact that Yichang is a preferred seat for convective cloud development;4)upper-level meso pressure fall system and vorticity factor enhancing the growth of the cloud.