The invention discloses a system and a method for carrying out steam turbine running by virtue of non-nuclear steam. The system comprises an isolation door for the outlet of a water feeding pump, a high-pressure heater bypass tube, an evaporator, a main steam door, an external steam inflation valve group and a pressure container. According to the method, a time needed for heating external steam to steam under running parameters by virtue of the heat generated by rotation of a main pump (main nuclear fan) is shorter (relative to a time needed for heating water to water under the running parameters), thus the running time is greatly shortened, and the test run construction period is shortened; and the external steam can be continuously supplied if the pressure of the external steam is greater than the minimum pressure needed for the running, the heat is generated by the rotation of the main pump (main nuclear fan) to further heat the steam to achieve running requirements. Therefore, the steam under the running parameters can be continuously supplied, thus continuous running of a steam turbine after achieving a constant speed is ensured, most of tests on the steam turbine in the constant-speed state are completed, the occupied time of a conventional island test on a nuclear power station after charging is reduced, and then the test run construction period of a nuclear power unit is shortened.