Abstract: The vibration signals generated by circuit breaker during operation contain lots of operating status information. In order to study the vibration signal characteristics of high-voltage circuit breaker under different working conditions, a 40.5 kV SF₆ single-phase sub-box circuit breaker mechanical vibration signal detection experimental platform is set up in the laboratory. The actual operating conditions are simulated by changing the air pressure, gas type and current carrying size of the circuit breaker filling gas. Meanwhile, the bad contact defect of circuit breaker is constructed and the vibration signal is analyzed by quantifying the contact state of circuit resistance tester. The results show that with the increase of air pressure, the amplitude of circuit breaker vibration signal changes rapidly and tends to increase. The amplitude of circuit breaker vibration signal is positively correlated with the current load, and the quadratic function between them is obtained by nonlinear fitting. The amplitude of vibration signal of circuit breaker is attenuated by both single gas and multi-gas mixture, in which the multi-gas mixture attenuates the signal amplitude less, while the single gas attenuates the signal amplitude more. When only the arc head of circuit breaker contacts, the amplitude ratio of vibration signal spectrum decreases in low frequency band, increases slightly in middle frequency band, and has no obvious change in high frequency band. The frequency with large amplitude is selected as characteristic frequency, and its corresponding amplitude is characteristic amplitude. The distribution of characteristic quantity can be used to characterize the contact state between contacts of circuit breaker.