The invention relates to a no-impact partition phase conversion system and method for an electric locomotive. The no-impact partition phase conversion system comprises a traction contact line, a pantograph and a locomotive transformer, wherein the pantograph obtains electric power from the traction contact line and then is connected with the locomotive transformer, then the locomotive transformer is connected with a load-side busbar, an electricity-receiving-side breaker is arranged on an electricity-receiving-side busbar, and a load-side breaker is arranged on the load-side busbar. The no-impact partition phase conversion system also comprises a partition inductor, a voltage detection module, a controller, a rectification inversion frequency conversion part and a vehicle-mounted electricity storage system, wherein the partition inductor and the voltage detection module are connected with the controller, the controller is connected with the rectification inversion frequency conversion part which is also connected with the load-side busbar, and a field circuit breaker is arranged between the rectification inversion frequency conversion part and the load-side busbar. According to the no-impact partition phase conversion system and method for the electric locomotive, provided by the invention, during partition phase conversion, the voltage of the locomotive transformer is converted into the next partition voltage, and switching-on field-circuit inrush currents for frequently switching the locomotive transformer are eliminated.