The invention discloses a convenient and reliable device for measuring the depth of engagement of circuit breaker contacts.The convenient and reliable device comprises six displacement sensors.The six displacement sensors are installed in internal counterbore holes of the six moving contacts of three phases A, B and C of a handcart type circuit breaker of a high-voltage switch cabinet respectively, power lines and signal lines are led out through circumferential gaps of the tulip contacts, led out of the high-voltage switch cabinet through space of the handcart type circuit breaker and connected with a data processing device, and the data processing device is connected with a display device.The convenient and reliable device is reasonable in structure, and measuring is convenient and accurate.