Vertical gravity gradient plays an important role in the research of the Earth’s gravity field. However, the measurement of the vertical gravity gradient is a hard work. With the fast development of the Earth’s gravity field modeling technique, it is possible to accurately approximate the vertical gravity gradient with the aid of the gravity field model as well as increasing gravity anomalies and rich terrain data. In the paper, a theoretical analysis was made on the computation of the vertical gravity gradient firstly, and then three methods, the gravity potential model method, the remove-restore method, and the point mass method, were used to accurately approximate the anomaly of the vertical gravity gradient. Tests of the three methods were made using some actual measurements of vertical gravity gradient over some area in China, and analyses were also made. Comparisons among the three methods show that the point mass method has the highest accuracy in approximation. At the end of the paper, some issues on the vertical gravity gradient to be further investigated were proposed.