Abstract: In order to meet the strong demand of synthesis impact sounds in sound source identification, a ball-plate collision model and corresponding fast computing method are given in time-domain. Firstly, a hybrid method combined finite-difference time-domain (FDTD) with modal expansion method (MEM) is used to solve the vibration equations of the plate. Secondly, some key issues for the hybrid method are considered, including modal truncation and initial value problem of MEM and consistency of different damping representation between two methods. Finally, the computing results using the hybrid method and that of FDTD for simply supported rectangular plate are compared, and the recording experiment for the L-shaped plate under free edges conditions is carried out. The results show that, comparing with FDTD the computing efficiency of the hybrid method is improved by 100 to 1200 times without loss of accuracy.