Abstract: The invention discloses a method for degrading phenol in industrial wastewater by a dual-frequency composite ultrasound, which belongs to the technical field of phenol degradation. The method adopts the dual-frequency composite ultrasound to perform ultrasonic treatment to a phenol solution to be degraded for 10-30 minutes. Degradation rate of phenol by the dual-frequency composite ultrasound can reach 83.74%, which is 45.23% and 51.11% higher than the degradation rates of a probe-type ultrasound alone and a tank-type ultrasound alone. Therefore, it can be clearly seen that the degradation effect of dual-frequency composite ultrasonic synergistic degradation of phenol in water is ideal.