The accuracy of regional gravity survey is directly affected by the precision of GPS altimetric survey. Using the CQG2000 quasi geoid model developed recently in China, the authors corrected the ellipsoidal height of GPS survey and, as a result, attained a higher accuracy of orthometric altimetric survey. With the method presented in this paper, a better result in 1:200000 regional gravity survey was achieved in the Three-River Drainage Area of Qinghai Province.