The power system serves as an important infrastructure in modern society, where circuit breakers play a crucial role as protective devices, swiftly interrupting abnormal currents to prevent severe electrical accidents. This research focuses on high-voltage circuit breakers, which handle currents reaching hundreds of kiloamperes. Due to the limited breaking capacity of individual arc chambers, high-voltage circuit breakers often adopt a multi-chamber parallel arc extinguishing structure. This structure not only impacts the performance during circuit interruption but also affects the steady-state operation of the circuit breaker. The large magnetic field generated by high current can cause significant eddy current heating, which poses a challenge to the heat dissipation ability of circuit breakers. In addition, it may also affect the operation of other structures connected to the circuit breaker. The arc chamber is one of the areas of highest magnetic field concentration within the circuit breaker. Adopting a multi-chamber parallel extinguishing structure can reduce the current in each chamber, decrease magnetic field intensity, and ultimately the steady-state operation ability of the circuit breaker can be improved. This study modified the number of parallel arc chambers in a high-voltage circuit breaker and compared the calculations of their magnetic field distribution. The computational results demonstrate the effectiveness of the improvements and elucidate the influence of parallel arc chamber quantity on the magnetic field distribution during steady-state operation of the circuit breaker.