Abstract: For the determination of high precise(centimeter level) local gravimetric geoid,it is very important to determine the terrain effects on geoid undulations.The effect of grid spacing of digital topographic model on terrain corrections and geoid undulations and the indirect terrain effect on geoid undulations are studied,as well as the effect of mass prism and mass line topographic models on terrain corrections.And the differences of the total terrain effect on geoid undulations by classical Stokes-Helmert method and Sjöberg's method are discussed and compared.Finally,some practical conclusions and suggestions are drawn from the test results of Hong Kong geoid determination.