Embodiments of the present application provide a pre-charging method of a power conversion device and a power conversion device. The power conversion device is used for a power conversion between a charging pile and a power battery and the method includes: receiving, by the power conversion device, a first message transmitted by a battery management system of the power battery, where the first message is used to indicate a charging readiness of the battery management system; and forwarding, by the power conversion device, the first message to the charging pile and performing a pre-charging, where the pre-charging includes charging a capacitor in the power conversion device. The technical solution in embodiments of the present application is capable of ensuring normal performing of a charging process.