Hematoporphyrin-conjugated magnetic graphene oxide nanocomposite was designed and prepared as a novel promising model. Fe3O4 nanoparticles were dispersed on the surface and edges of the graphene oxide in a uniform size, and hematoporphyrin was effectively conjugated onto graphene oxide via hydrophobic interactions and π-π stacking. With the photosensitivity of hematoporphyrin and the magnetic properties of Fe3O4 nanoparticles, it can be applied for photodynamic therapy to increase the accumulation of hematoporphyrin in tumor cells. The cytotoxicity in vitro showed that hematoporphyrin conjugated magnetic graphene oxide nanocomposite irradiated at 671 nm generated cytotoxic singlet oxygen and exhibited a good inhibition to the human tumor cell HeLa (IC50 = 10.12 µg/ml), which suggested that the nanocomposite is potential for targeting photodynamic therapy as a promising drug delivery system.