The CT20 spring operating mechanism is widely used in 126 k V voltage level circuit breakers because ofits series of advantages. This type mechanism may not meet the requirement of higher interrupting capacity circuitbreaker while the interrupting capacity is increasing. If the corresponding measures are not taken

the vibration ofthe closing latch during the closing of the mechanism may result in the failure of the closing operation. In view of thisproblem

the vibration of the closing latch during closing is chosen as the research point. First

the closing process isanalyzed by simulation software. Then the vibration of the closing latch is recorded by the high speed camera. Finallythe effect on closing perform caused by the vibration of the closing latch is analyzed and the research result is summa-rized.The method of reducing the vibration of the closing latch is proposed. From this paper some conclusion can begot:The vibration time of closing latch always continue 10 ms which is the key of closing keep process. The ampli-tude coefficient of the bigger closing latch is 7.6% with that of the smaller one is 28.6%. Closing keep process may failwhile amplitude is too big or vibration time is too long.