The invention discloses a method of using earth gravitational field to evaluate gravity sensor resolution. On the surface of the earth, a gravity acceleration value and a position height thereof are in a linear relation, and then the earth gravity acceleration values at different positions are measured by changing the height of the gravity sensor, and the theoretical increments of the gravity acceleration values at the different heights are calculated, and the increments of the actual gravity accelerations of different heights are measured. According to GJB1037-2004, when the ratio between actual gravity acceleration increments and the theoretical increments is greater than 50%, and the resolution is qualified, and therefore the resolution of the gravity sensor is evaluated. By controlling the distance changes of the heights of the gravity sensor accurately, the weak change of the input gravity acceleration is realized, and then the gravity sensor having the resolution better than 0.1mGal is evaluated, and the feasibility of the method is strong.