Local or regional geoid refinement is the primary commission for the elevation datum. Taking the GPS network of Songyuan irrigation area as an example, this paper refined the local geoid based on the quadratic surface fitting and spatial interpolation of height anomaly, and on the same algorithms of residuals between height anomaly and geoid undulation of EGM2008 with the remove-compute-restore method. The results indicated that the precision of the local geoid refined by the residuals were higher than that refined by the height anomaly. The precision of geoid refined by residuals using quadratic fitting, TPS and KRIGING was similar, and higher than the TPS. The comparison between height anomaly and geoid undulation of EGM2008 showed that the state 1985 height datum and the global datum of EGM2008 had a mean difference of 0.326 m, with the standard deviation of 0.047 m, which indicated that EGM2008 has a relatively higher precision and important significance for the refinement of regional and state geoid.