<p>The breaking capacity of a circuit breaker is crucial for ensuring the safe operation of the power grid system. Investigating the role of the interrupting speed in its breaking capacity has significant engineering value for optimizing the design of high-voltage equipment. Taking a 252 kV circuit breaker as the research object, this study combines high-speed camera motion characteristic detection with electromagnetic-thermal-flow multi-physical field coupling simulations to systematically investigate the regulation mechanism of interrupting speed on the circuit breaker’s breaking capacity. The focus is on analyzing the spatial-temporal distribution characteristics of current density and the evolution of the contact surface temperature field under different speed gradients. The results show that the interrupting speed is positively correlated with the rate of decrease in current density, but there exists a critical speed threshold. Beyond this threshold, the turbulence separation effect leads to the concentration of arc energy. With a 20% increase in interrupting speed, the fluctuation amplitude of the contact surface temperature is reduced by 35%, while low-speed conditions are prone to multiple temperature fluctuations, leading to arc re-ignition. The research results reveal the regulation mechanism of interrupting speed on the circuit breaker’s breaking capacity, providing theoretical support for the design of breaking parameters in high-voltage circuit breakers.</p>