Abstract: Gravitational field and its variation with time accurately were surveyed in detail.The polar motion and length-of-day(LOD) changes are known to cause the temporal variations in the gravitational field.The effects of the earth’s rotation on the geopotential coefficients,gravitational perturbs and vertical deviation is modeled.It is numerically estimated,with these models,the changes in the gravity observations of some sites.We derive the formulas of the geopotential coefficients 12 and 12 for EGM96 model.The results suggest that the series of effects on the gravitational field due to the variations of the earth’s rotation should be accounted for in high-precision space geodesy.