Intelligent circuit breaker is an importance part of intelligent substation. This paper introduce the on-line monitoring key technology

design method for mechanical characteristics of indoor 12 kV（VS1） vacuum circuit breaker

and introduce difficulty and difference in design for on-line monitoring and off-line test. Keystone analysis and experiment design on the application of the angle sensor and beeline sensor use in on-line monitoring

and it is considered that the theorical test of angle sensor can meet the test requirements

but for machining parts and installation requirements are relatively high. Due to the beeline sensor is mounted directly to the direction of movement of the movable contact

can most directly reflect the circuit breaker travel/time characteristic. So the test precision and consistency are good

which can meet the industrial mass production. The quantity produced as the result of one operation satisfy industry manufacture. Sampling method of current close-open and auxiliary switch close-open and vibration sensor expatiate for moment-open and moment-close. The results show that

vibration sensor meet the requirements of use.