Abstract: Relative accuracy of regional gravimetric geoid (quasi-geoid) determination is estimated by an analytical method, which is determined by regional terrestrial gravity measurements and geopotential model. First, the accuracy relationship between terrestrial gravity measurements and spherical harmonic coefficients is deduced based on the Stokes formula. Second, based on the truncated approach of “remove-restore” and spherical harmonic expansion of the covariance function, the analytical relationships among errors of inner terrestrial gravity measurements, errors of outer geopotential model and relative accuracy of regional gravimetric geoid are deduced respectively. Thirdly, for convenience of calculation, it is proposed that frequency truncation errors of inner terrestrial gravity measurements and outer geopotential model be merged and then reclassified in two parts: ① at frequencies higher than inner gravity data in global area, ② at frequencies between inner gravity data and geopotential model in outer area. They are estimated respectively by using empirical degree-variances model. Simulation indicates the corresponding relationships among terrestrial gravity measurements accuracy, resolution and integral radius, geopotential model accuracy and resolution and the relative accuracy of regional gravimetric geoid (quasi-geoid) determination.