A variety of surgical methods have been practiced to treat the Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome. One of the latest minimally invasive methods is using surgisis soft tissue graft to cover the dissected space. Few reports about the vault neoplasm and no pathological results after this new operation are seen. Accordingly, the authors herein describe a patient with a vault polyp after vaginoplasty using surgisis soft tissue graft, whose pathological result was unexpected smooth muscle tissue. The authors believe it is possible that the cytokines in the graft are associated with the smooth muscle neoplasm or the fibroblasts transform into smooth muscle cells. In this article, we firstly report the pathological result of the vault polyp after vaginoplasty using biomaterials and discuss its cause with details. According to what they observed and the pathological results, they report a novel side-reaction of this biomaterial for vaginoplasty.