The coupling numerical model between astronomical tide and tsunami was built on the data of COMCOT model,which was verified by the Japanese "March 11" tsunami. And the tsunami source of Manila seismic tsunami was designed and computed to analyze the risk of tsunami which may happen in the Guangdong seacoast. According to the results,the maximum quantity of water increasing and the time of the tsunami arriving the Guangdong seacoast was calculated. The coupling simulation between astronomical tide and tsunami has significant meaning for evaluating the risk and early-warning of tsunami in the area of the Guangdong coast.