We have constructed are gional Bouguer gravity anomaly map using marine and land data from Tai wan and the Chinese province of Fuchien, as well as SEASAT altimetry-de rived gravity data for the Tai wan Strait and its surrounding area. The map shows isogals trending generally in a NE-SW direction, conforming with the over all shallower geo logical strike of the strait. Removing gravity effects generated by the water layer and seafloor to pography, the regional Bouguer gravity anomaly is obtained, reflecting the subsurface structure. Moho depth is then computed by the Parker-Oldenburg iterative method from the regional Bouguer gravity data set. Over the strait area, the geometry of the Moho relief is smooth with an average depth of about 30 km, except for the Penghu up lift. Moho depth is shallower in the Taiwan Strait and thickens to ward both sides of the strait. The relatively shallower Moho depth, reaching up to 28 km, is convex up ward underneath the Penghu uplift.