The invention relates to a high-adaptive charging system and method for an electric vehicle. The system comprises a power battery pack, a battery management system, a charging interface, a charging positive relay, a charging negative relay and a structure conversion relay group, wherein the charging positive relay comprises a positive relay in a common charging mode, a positive relay in a high-voltage charging mode, and a positive relay in a low-voltage charging mode. The structure conversion relay group controls the series-parallel connection structure of the battery pack, adjusts the charging voltage of the electric vehicle, and adjusts the charging voltage of the battery pack under the allowable charging current of a charger in order to adapt to a connected charging pile. For a high-voltage high-power charger, the system increases the charging voltage of the battery pack and the charging power of the battery pack, shortens the charging time, and improves the adaptability of the electric vehicle to long-distance driving. For a low-voltage charger, the system reducing the charging voltage of the battery pack, makes the battery pack compatible with the low-voltage charger, and reduces the dependence of the electric vehicle on general charging infrastructure.