The selfattraction effect (SAE) is an important systematic error in a highprecision atom interferometry gravimeter, which has been researched. In this paper, we use the finite element method (FEM) to calculate the SAE of an atom gravity gradiometer. In this way, the SAE of the gravity gradiometer is accurately determined, and the calculation result shows this effect is 235(8) E (1 E = 1×10 −9 s −2 ) in the atom gravity gradiometer. Based on this calculation, this effect in many highprecision experiments can be corrected.