Abstract: Microorganisms can photoreactivate after ultraviolet radiation on the effluent from WWTP. The effect of ultrasonic co-action on controlling E.coli′s photoreactivation after UV disinfection is studied in this essay. It is found that there is a good linear relationship between UV irradiation dose and E.coli′s inactivation rate,and the interrelated coefficient is 0.99. When US coaction on UV as pretreatment,E.coli′s photoreactivation rate can decrease by 59% with the same energy consumption,while energy consumption can decrease by 50% with the same photoreactivation rate. Considering economics and microorganisms security,US-UV is regarded as efficient and feasible for wastewater disinfection.