Abstract: This paper studies the problem on extending the method for fitting between terrestrial gravity quasi-geoid and GPS leveling quasi-geoid to the case of sea area near coast. In theory, it is proved that marine geoid can not coincide with the corresponding quasi-geoid if sea surface topography (SST) exists, and a formula is derived for calculating the difference between marine geoid undulation and corresponding height anomaly. The formulas are presented to calculate the normal height of mean sea surface (MSS) on a local vertical datum and altimetric quasi-geoid. Considering the fact that altimetric MSS can have about the same accuracy level as that of GPS geodetic height, an extended method for fitting marine gravity quasi-geoid to altimetric quasi-geoid on a local vertical datum is advanced by using altimetric MSS data.