The basic features of climatology and interannual variations of tropical Pacific and Indian Oceans were analyzed using a coupled general circulation model(CGCM),which was constituted with an intermediate 2.5-layer ocean model and atmosphere model ECHAM4.The CGCM well captures the spatial and temporal structure of the Pacific El Nifio-Southern Oscillation(ENSO)and the variability features in the tropical Indian Ocean.The influence of Pacific air-sea coupled process on the Indian Ocean variability was investigated carefully by conducting numerical experiments.Results show that the occurrence frequency of positive/negative Indian Ocean Dipole(IOD)event will decrease/increase with the presence/absence of the coupled process in the Pacific Ocean.Further analysis demonstrated that the air-sea coupled process in the Pacific Ocean affects the IOD variability mainly by influencing the zonal gradient ofthermocline via modulating the background sea surface wind.