The invention discloses a method for double-frequency composite ultrasonic degradation of phenol in rural sewage, and belongs to the technical field of phenol degradation. According to the method, double-frequency composite ultrasonic treatment is adopted to perform ultrasonic treatment on a to-be-degraded phenol solution for 10-30 min; the double-frequency composite ultrasonic degradation rate onphenol can reach 83.74%, and is improved by 45.23% and 51.11% compared with the degradation rate of single probe type ultrasonic treatment and single groove type ultrasonic treatment. Therefore, it is obviously shown that the degradation effect of dual-frequency composite ultrasonic synergistic degradation on phenol in water is ideal.