Abstract: Photodynamic therapy (PDT) is a therapeutic strategy by which photosensitizers are excited by specific light irradiation to produce singlet oxygen for killing the surrounding cells. The advantages of PDT include weak invasion, slight side effect, and low resistance. The advantages of nanoscale drug delivery systems (DDS) include tumor-targeting, sustained release, and environmental-sensitivity. The combination of PDT and nanoscale DDS would likely lead to tumor targeting of photosensitizers and enhance their antitumor effectiveness. This review discusses the mechanism of PDT, photosensitizer-loaded nanoscale formulations, the combination of PDT and other antitumor therapies, and summarizes the applications and prospects of anti-tumor nanoscale DDS based on PDT. This review is a useful reference for its clinical application.