The TiO₂NPs and Zn-N-TiO₂NPs with different doping concentrations were synthesized by sol-hydrothermal method using butyl titanate， zinc nitrate and ammonia as titanium source，Zn source and N source，respectively.X-ray diffraction（XRD），Raman spectra，scanning electron microscope（SEM），UV-visible absorption spectroscope（UV-vis） were used to characterize the nanoparticles in various groups.Cure Rite radiometer was used to characterize the dental light emitting diode curing lamp.The Streptococcus mutans were divided into blank control group，LED light irradiation group，TiO₂NPs group，1%Zn-3%N-TiO₂NPs group（Zn1 group），3%Zn-3%N-TiO₂NPs group（Zn3 group），5%Zn-3%N-TiO₂NPs group（Zn5 group），and 7%Zn-3%N-TiO₂NPs group（Zn7 group）.The nanoparticles in each group were mixed with Streptococcus mutans bacteria solution（the final concentration of nanoparticles was 2 g·L^－1） and were shaken well.The nanoparticles groups and the LED light irradiation group were exposed to dental LED light for 1， 3，and 5 min，the blank control group was treated with culture medium only，and the number of colonies in each group was recorded by plate colony counting method.The group with the best antibacterial effect（Zn3 group） was selected.The reactive oxygen species（ROS） release amount was detected using DPBF probe，and the experiment was divided into 0 min group， 1 min group， 3 min group and 5 min group.A total of 100 μL Zn3-DPBF solution at the concentration of 2 g·L^－1 in each group was selected for dental LED light irradiation for 0， 1， 3 and 5 min， respectively， and the changes in absorption peaks at 410 nm were observed，indicating the ROS release amount.In the experiment exploring the influence of N-acetyl cystethione（NAC） in the inhibitory effect of Zn3 combined with LED light irradiation on Streptococcus mutans，Streptococcus mutans were divided into control group， 5 mmol·L^－1NAC group，Zn3 group and NAC +Zn3 group.After LED light irradiation for 5 min and culture avoiding light for 24 h，plate colony counting method was used to record the number of colonies in each group.

Zn-N-TiO₂NPs was successfully synthesized and its crystal structure was anatase.The average sizes of nanoparticles in TiO₂NPs group，Zn3 group，Zn5 group and Zn7 group were 15.6， 11.3， 9.8， 9.4 and 7.3 nm， respectively.The SEM results showed that the nanoparticles were spherical particles with uniform distribution.The Uv-vis results showed that the absorbance（A） value of Zn3 was increased significantly in the wavelength range of 400－500 nm.Compared with blank control group， the colony count in Zn3 group was the least when LED irradiation was 5 min（P<0.05）.Compared with 0 min group，the absorption peaks of Zn3-DPBF solution at 410 nm in 1 min，3 min and 5 min groups were decreased successively， indicating the ROS relaease amount of nanoparticle solution in various were increased with the prolongation of illumination time.Compared with Zn3 group，the number of colonies in NAC+Zn3 group was significantly increased（P<0.05）.

3%Zn-3%N-TiO₂NPs combined with LED light irradiation can effectively inhibit the growth of the Streptococcus mutans through photocatalysis.