In this work, simple raw materials and reaction conditions were used to synthesize a versatile nanoprobe using a one-step method. Graphene quantum dot (GQD) and gold chloride were mixed and irradiated with ultra-violet (UV) radiation for 1 min. Then, the gold nanosphere cluster with the diameter of 50 nm and coated using GQD was formed using a facile one-step approach. GQD played the roles of reducing agent, stabilizer and drug carrier instead of a harmful reducing agent or stabilizer. The nanoprobe had good dispersion, stability, excellent photoacoustic imaging (PAI) and computed tomography (CT) imaging performance, low cytotoxicity and photothermal conversion efficiency of up to 51.31%. The results for cell and animal experiments showed that targeted PAI/CT imaging of tumor after modification of folic acid (FA) could be obtained using the probe. Meanwhile, after the adsorption of doxorubicin, the chemo-photothermal combined therapy for tumor could be carried out through controlled drug release from GQD under heated and acidic environment of tumor. Additionally, the treatment effect was significantly superior to single modes. The body weight, Hematoxylin and Eeosin (H&E) staining of main organs and blood biochemical indicators showed that the probe had good biological safety after injection. The current work proposes a new dual-mode bio-imaging and chemo-photothermal combined therapy nanoprobe, which presents good application prospect for tumor theragnostic.