Designing a multifunctional nanomedicine for integration of precise diagnosis and effective treatment of tumor is desirable but remains a great challenge. Here, we reported a multifunctional nanomedicine based on WS2 quantum dots (QDs) which was prepared by a facile and 'green' method through physical grinding and ultrasonication. The as-obtained WS2 QDs with small size (3 nm) possess not only significant X-ray computed tomography (CT)/ photoaccoustic imaging (PA) signal enhancement but also remarkable photothermal therapy (PTT)/ radiotherapy (RT) synergistic effect for tumor treatment. With CT/PA imaging and the synergistic effect between PTT and RT, the tumor could be accurately positioned and thorough eradicated in vivo after intravenous injection of WS2 QDs. Moreover, hematoxylin & eosin (HE) staining, blood hematology and biochemistry analysis revealed no noticeable toxicity of WS2 QDs in vitro and in vivo, which confirmed that WS2 QDs possess well biocompatibility. This multifunctional nanoparticle could play an important role in facilitating simultaneously multimodal imaging and synergistic therapy between PTT and RT to achieve better therapeutic efficacy.