The main objective of the study is to explore how ultrasonic work with ultraviolet, in an attempt to find out the synergistic effect in controlling the phenomenon of microbial photoreactivation, as well as to analyse the feasibility of synergistic disinfection and related theories. Two different frequencies of ultrasonic transducers (28/40kHz)were used in combination with ultraviolet for secondary effluent disinfection. By controlling the process parameters that may contribute to the efficiency of synergistic disinfection, such as different reaction time, respective ultrasonic and ultraviolet dose. The results show that the synergistic disinfection of ultrasonic and ultraviolet can inhibit such a phenomenon, while maintaining continuous disinfection ability of ultraviolet. Ultrasonic has great potential in enhancing continuous sterilization abilities of ultraviolet. Synergistic disinfection has great advantages compared with other disinfection technologies and has a promising prospect in future use.