The 2006 dual Pingtung earthquake event and the 2004 South Asia tsunami highlighted the potential tsunami hazards from Manila trench. Manila trench is only about 100 km away from Taiwan, therefore one shall punctuate the importance of thorough study on all possible tsunami scenarios for hazard mitigation. Based on the faults parameters issued by USGS and the seismic record from Global CMT, this study creates a hypothetical earthquake tsunami scenario caused by seismic motion at Manila trench. The magnitude of the earthquake is 9.35 ( Mw), the total length is 990 km, and the maximum initial free-surface height is 9.3 m. The initial displacement profile is provided in this paper. An open source code, COMCOT, is adopted to perform the simulation of the tsunami propagation, runup, and inundation around Taiwan. Nested grid system and moving boundary technique are adopted to study runup and inundation. The result shows that the maximum wave height is 11 m in southern Taiwan. Serious flooding is observed in the southwest coast of Taiwan. Tsunami inundation is able to reach 8.5 km inlandward. Due to the refraction effect, 8 m wave height is noted in the northeast coast of Taiwan. The detailed tsunami behavior around Taiwan is described in the context.