Modern satellite altimetric gravity (SAG) is studied in this paper on the basis of a comparison with measured data on spatial resolution, on-shore and off-shore joint mapping, and interpretation work in the South Yellow Sea. It is pointed out that resolution of high resolution satellite altimetric gravity data can now achieve 4×10^-5m/s²l or so and thus can be used in 1∶1 million regional marine gravity survey. Suggestions on marine gravity work for marine oil and gas resources and geological survey in China are also put forward in this paper.