This paper outlines the monitoring system of the entire switchgear, while the monitoring system of high-voltage circuit breakers is described in detail. The measured quantities and the method of displaying the measured quantities (graphically, numerically) are listed. The external influence on the monitoring system of high-voltage circuit breakers and the methods of protecting the protected object (circuit breaker) are also described. The main characteristics and designs of the monitoring systems of high-voltage circuit breakers manufactured by Siemens, ABB and Koncar are presented.