Abstract: Aim at the problem that a coal mine safety monitoring system cannot accurately sense the power-off state of a controlled object due to the fact that the output wire of a mine-used contact detection feed breaker is wrong, this paper introduces a self-diagnosis circuit based on fixed frequency DC pulse, gives the circuit principle, designs the fixed frequency DC pulse signal generator and contact pulse fusion signal detection circuit, and introduces the program design of self-diagnosis breaker from two aspects of feed power-off detection process and wiring state self-diagnosis process. The mining breaker with surface self-diagnosis function can effectively identify the output wiring error of the breaker and ensure the reliability of the feed signal.