The impact of ultrasonic on the aerobic biochemical degradation efficiency of refractory organic wastewater and sludge reduction was studied through dealing with the sewage and sludge which were from a vitamin C manufacturing factory using the special high -power ultrasonic generator. The results showed that:high power and long ultrasonic treatment time to the contact oxidation tank inlet sewage could remove 56% of the COD, and increase B / C ratio from 013 to 022. The ultrasonic treatment to the Plug flow aeration tank inlet sewage could remove 33% of COD and B/C ratio was more than doubled -from 011 to 023- . Furthermore, ultrasound treatment could reduce settling volume of the second settling ponds after contacting the oxidation tank, and promote some material, which is easily degradated in the residual sludge of sludge well, to transfer from solid to liquid to achieve the purpose of sludge reduction.