Sonodynamic therapy (SDT) has attracted wide attention for its high tissue-penetration depth capacity. However, developing new kinds of sonosensitizers that are capable of generating large amounts of reactive oxygen species (ROS) still remains a challenge. Herein, covalent organic framework-titanium oxide nanoparticles (COF-TiO2 NPs) were successfully synthesized by using COF as a template. Under ultrasound (US) irradiation, large quantities of ROS can be generated, and compared with pure TiO2 NPs, the SDT performance of COF-TiO2 nanoparticles was significantly improved due to the narrower band gap. Both in vitro and in vivo experiments demonstrated the great tumor inhibitory effect via COF-TiO2-mediated SDT. This work broadens the biomedical applications of COF-based composites.