Impacts of regional sea surface temperature anomaly (SSTA) on the interdecadal variation of the Northwestern Pacific Subtropical High (NWPSH) are studied by numerical simulation with the NCAR CAM3 global atmospheric circulation model drived by 1950－2000 monthly SST in different sea areas (global, extratropical, tropical, tropical Indian Ocean－Pacific, tropical Indian Ocean, and tropical Pacific), in comparison with observational data. Results suggest that the change in the global, tropical, tropical Indian Ocean－Pacific, and tropical Indian Ocean SST has great effect on the interdecadal variation of the subtropical high. The SST in these sea areas varies, the interdecadal variation of the subtropical high occurs in the middle－late 1970s, followed by its area enlarging, its intensity enhancing, and its position more westward or southward than normal, which is in better concord with observations; the variation of the tropical Pacific SST also influences the interdecadal change of NWPSH in summer, and as a result, the high’s area and strength change in the late 1960s on an interdecadal basis and its southern border undergoes interdecadal variation in the middle－late 1970s, afterward, the high’s intensity enhances, its area enlarges and its location is south of mean, which is opposite to the weaker impact offered by the extratropical SST. The variation of NWPSH driven by the SST in the tropical Indian Ocean is more consistent with the observations and more significant on the interdecadal scale than that driven by the SST in the tropical Pacific Ocean, and a possible reason is due to the contrast of anomalous circulation over the Bay of Bengal-Southeast China between them, with the former exerting anomalous anticyclone in favor of the intensity enhancing and enlarging and westward extension of the area, and the latter exerting anomalous cyclone unfavorable to the westward extension of the area. As a background, the interdecadal variations of the tropical Pacific and Indian SSTs occurring in the late 1970s have important effects upon the equivalent scale change in the NWPSH.