The main method for melanoma is photodynamic therapy (PDT), and the design of more efficient photosensitizers is the key point to melanoma therapy. To promote the therapeutic effect of PDT, a novel photosensitizer was designed. The substrate was the Protoporphyrin IX (PpIX), then the demethylated drug SGI-1027 and PpIX were encapsulated by the synthesized PMHC₁₈-mPEG to form the SGI@PpIX-mPEG complex system. PpIX exposed to illumination causes cells to produce a large amount of reactive oxygen species (ROS), which would increase the content of the downstream protein Caspase-3. The demethylated drug increases the content of GSDME. Research indicates that the synthesized novel photosensitizer drug can not only generate reactive oxygen species to kill cancer cells, but also further lead to pyroptosis and enhance the effect of photodynamic therapy through the interaction between Caspase-3 and GSDME.