The present application provide a power supply control method for a power conversion apparatus, where the power conversion apparatus is configured to conduct a power conversion between a charging apparatus and a power battery, the method includes: conducting a power-on self-test with the charging apparatus of auxiliary power by the power conversion apparatus; determining a power supply priority order of the charging power and the power battery on the basis of a state parameter of the power battery under the condition that the self-test of the power conversion apparatus succeeds; determining the one of the charging power of the charging apparatus and the power battery with a higher power supply priority as a current working power of the power conversion apparatus by the power conversion apparatus. The method of the present application can provide a stable working power for the power conversion apparatus without additional power supply device.