In 2009, Typhoon Morakot brought heavy rainfall and severely damaged the mountainous area in Taiwan. The Hsien-du-shan rock avalanche occurred at ChiaHsien Township, Kaohsiung County, Taiwan, destroyed the Hsiaolin Village and killed more than 400 local residents. The case highlighted the great importance to identify the location and precursors of a possible rock avalanche. In this study, the initiation of the Hsien-du-shan rock avalanche is simulated by a discrete numerical analysis method, callcd Discontinuous Deformation Analysis (DDA). The simulation indicates that two slope failures occurred at the Hsien- du-shan rock avalanche due to the geometry of the sliding surface. The sliding rocks and soils can be briefly divided into two groups. The computational results fit well to the local information, which two giant bursts were heart during the slope failure. However, the time interval of the two slope failures in DDA was very short. Therefore, the slope failure can be also considered as a massive one.