In this study, MoS2 nanodots modified TiO2 (P25) composite photocatalyst (MoS2/P25) was fabricated via a facile liquid ultrasonic mixing method. Compared to the pure P25, the MoS2/P25 exhibited improved photocatalytic degradation activity under simulated sunlight with rhodamine B (RhB) and methylene blue (MB) as the target pollutants. RhB or MB (40mL 10mg/L) completely degraded within 20min, and the kinetic constant reached 0.221 and 0.253min−1 for RhB and MB, respectively. Based on the characterization of transient photocurrent response measurement and UV–vis diffuse reflectance spectra, a possible photocatalytic mechanism was proposed. The enhanced photocatalytic performance was attributed to the heterostructure of P25 and MoS2 nanodots, improving their charge separation and enhancing their absorption capacity to the full sunlight spectrum. We believe that this study will contribute to the development of new photocatalysts and improving the catalytic performance of traditional photocatalysts.