Thermal management system and heating method of battery pack

The invention belongs to the technical field of battery packs, and particularly relates to a thermal management system of a battery pack. The system comprises an engine heat dissipation loop used for cooling an engine; a motor and electric control heat dissipation loop which is used for cooling the motor and electric control elements; and a liquid cooling plate which is used for adjusting the temperature of the battery pack, wherein the engine heat dissipation loop and the motor and electric control heat dissipation loop are connected to the liquid cooling plate through a reversing valve. According to the technical scheme, the first cooling liquid in the engine heat dissipation loop can be used for collecting waste heat of the engine, or the second cooling liquid in the motor and electric control heat dissipation loop is used for collecting waste heat of the motor and electric control elements, and the first cooling liquid or the second cooling liquid can directly enter the liquid cooling plate to heat batter