Abstract: Objective To prepare ferric hydroxyl oxide (FeOOH) nanorod modified with graphene quantum dots (GQD) and polydopamine (PDA) and investigate the in vitro photothermal antitumor properties. Methods GQD-modified and PDA-coated FeOOH composite nanomaterials were prepared and their physical and chemical properties, such as particle size distribution, microstructure, composition and photothermal conversion efficiency, were evaluated. The antitumor properties of the obtained nanomaterials in SKOV3 ovarian cancer cells were invesigated under the irradiation of near infrared laser. Results Compared with FeOOH before modification, the photothermal properties of the resultant nanocomposite were significantly improved, with good photothermal properties. According to in vitro cell experiments, the composite showed good inhibitory effects on ovarian cancer cells which could be used in the photothermal therapy of tumor. Conclusions The composite nanomaterials prepared by this method have excellent biocompatibility and photothermal conversion properties, and are expected to be a new photothermal therapy reagent for tumors.