The forward calculation method and the conclusion of the gravity and the gravity gradient variation of the artificial mass body can be used as the mathematical foundation to precisely describe the gravity and gravity gradient variation. It can be used to test and calibrate the gravity gradient measurement device. Compared with the square body mass, the gravity variation generated by the spherical mass is similar to that of the total mass focused on the centroid. It is easy to calculate and apply. For this purpose, the spherical shape artificial mass body is used as the analysis object of gravity excitation to form a forward calculation method.