In the interruption process of a DC circuit breaker, the arc plasma inside the extinguishing chamber is influenced by the inter-pole magnetic field, resulting in motion that directly affects the interrupting performance of the DC circuit breaker. To explore the impact of the inter-pole magnetic field in multi-pole series DC circuit breakers, we utilized the finite element simulation software Maxwell to model the magnetic blowing forces within the extinguishing chamber system of a DC molded case circuit breaker, considering two positional states: when the contacts are just opened and when the arc moves into the arcing chamber. This study aims to investigate the effects of magnetic blowing forces on the arc in the context of multi-pole series configurations. By calculating the magnetic blowing forces acting on the arc in three different directions under various current and pole spacing parameters for a two-pole series DC molded case circuit breaker, we derived the arc's deflection angle. Additionally, by integrating the spacing of the gas-producing components of the circuit breaker, we assessed the risks associated with current interruption. This work provides a valuable reference for the advancement of circuit breakers toward higher current capabilities and miniaturization.