The invention discloses a broadcast cutting method and system applied in television relaying. The method comprises the following steps that locations needing upper broadcast cutting and lower broadcast cutting are recognized in a television program signal; audio watermarks are added at the locations needing upper broadcast cutting and lower broadcast cutting; a television program added with the audio watermarks is transmitted to a relay station; when the relay station broadcasts the television program, the audio watermarks are monitored and analyzed; when the audio watermark of upper broadcast cutting is analyzed, the broadcast television program is switched into a local program; when the audio watermark of lower broadcast cutting is analyzed, the broadcast local program is switched into the television program. According to the method, automatic broadcast cutting is achieved, the control mode is simple, convenient to operate and efficient, and pressure of operating personnel in manual control is relieved.