Dental caries, recognized as one of the most prevalent oral diseases, exhibits a strong correlation with Streptococcus mutans. Manganese tungstate (MnWO_x) nanoparticles enriched with oxygen vacancies were synthesized via an organic phase method followed by calcination. The morphology and structure of MnWO_x nanoparticles before and after calcination were thoroughly characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results revealed that MnWO_x calcined at 400 °C for 1 hour possessed the highest proportion of oxygen vacancies while maintaining a similar morphology compared with uncalcined sample. Probe tests were employed to assess the ability of MnWO_x in generating ₁^O₂ and .OH radicals after ultrasonic activation, demonstrating that an increase in oxygen vacancies significantly enhanced the radical-generating capacity of MnWO_x. Antibacterial experiments demonstrated that MnWO_x-PEG under 5 minutes of ultrasonic exposure could eliminate 70.57% of Streptococcus mutans, while MnWO_x-PEG under 10 minutes of ultrasonic exposure could eradicate 80.57% of Streptococcus mutans within a biofilm. These findings suggest that the sonodynamic approach for oral antibacterial and anti-biofilm treatment offers a novel and promising strategy for the prevention of dental caries and the promotion of oral health.