Despite wide application of vertical anti-seepage reinforcement in embankments, the effectiveness of anti-seepage is difficult to be detected and evaluated after the anti-seepage project is finished due to the complexity of geological conditions and concealment of project. In this paper we analyzed the effects of vertical anti-seepage body, the depth, damage location, and integrity of anti-seepage body on the seepage field of levee by numerical simulation taking the regulation project of diverting Huaihe River into Xinyi River as a case study. We further examined the effectiveness of anti-seepage body by comparing the hydraulic gradient of spill point with the allowable hydraulic gradient of soil. Results show that the head behind the anti-seepage body decreased markedly after the vertical seepage control treatment was carried out on the levee. The bottom of anti-seepage body inserting into the clay layer of levee had better impervious effect than that of anti-seepage body not inserting into clay layer. In the presence of defectives, the infiltration line rose obviously behind the anti-seepage body. The hydraulic gradient in all conditions at the spill point was smaller than the allowable hydraulic gradient, indicating evident seepage control effect.