This article focuses on the early warning and prevention technology of thermal runaway in the battery management system of new energy vehicles. Firstly, analyze the thermal runaway mechanism of lithium-ion batteries, including the chain reaction triggered by mechanical, electrical and thermal abuse, and explore the influence of materials, structure, charge and discharge strategies and environmental factors on safety. Secondly, sort out the evolution path of battery management system thermal runaway early warning technology from threshold model to artificial intelligence-driven, and propose an optimization scheme of multi-parameter fusion and multi-physical field coupling; Finally, through case analysis, prevention and control strategies are proposed from four aspects: design, balance, thermal management and operation and maintenance. It is pointed out that sensor accuracy, algorithm robustness and standard uniformity are the technical bottlenecks.