The invention relates to a circuit breaker with a pressure relief function. The circuit breaker comprises a shell, and a pressure relief opening is formed in the shell. The circuit breaker further comprises a pressure relief cover which covers the pressure relief opening and is connected with the shell. An exhaust hole used for being communicated with the pressure relief opening is formed in the pressure relief cover. A sealing ring is arranged at the pressure relief opening, and a blocking piece for blocking the pressure relief opening by pushing against the sealing ring is movably arranged at the pressure relief opening. An elastic piece used for applying an elastic force to the blocking piece to block the pressure relief opening is arranged in the pressure relief cover. When the pressure of gas in the shell is larger than the elastic force of the elastic piece to the blocking piece, the blocking piece unblocks the pressure relief opening so that the pressure relief opening can be communicated with the exhaust hole to relieve pressure. When the pressure of gas in the shell is smaller than the elastic force of the elastic piece to the blocking piece, the elastic piece pushes against the blocking piece to block the pressure relief opening. The pressure relief structure on the circuit breaker can be repeatedly used, and the use cost of the circuit breaker is reduced.