The invention discloses a low frequency breaker with a phase-selection brake-separating function. The low frequency breaker comprises a signal acquisition circuit, a signal processing circuit, a control system circuit, an operating mechanism and a low frequency breaker body, wherein the signal acquisition circuit measures three-phase voltage and current of a system and contact separating brakes of the breaker body, the signal processing circuit completes processing of signals measured by the signal acquisition circuit, the control system circuit receives signals processed by the signal processing circuit, completes analysis of phase angles and phase difference of three-phase voltage and current signals, and sends out instruments to respectively control the three-phase operating mechanism to move according to analysis results, the operating mechanism separates or closes a brake of the breaker body according to received instruments, and the low frequency breaker body is used for a frequency division power transmission system. Simultaneously, the breaker further compensates voltage of the environment temperature and a motor control loop and delay of the mechanism caused by the voltage, finally opens a contact at a specified current phase angle, and reduces impacts of brake-separating operation on the system.