Aiming at the technical bottlenecks of traditional new energy vehicle battery management systems (BMS) in terms of monitoring accuracy, thermal management performance, energy balancing efficiency and operational reliability, this paper conducts multi-objective optimization design. By building a precise monitoring system, developing an air-cooled-liquid-cooled coupled thermal management system, optimizing the bidirectional DC/DC energy balancing technology and modular redundant architecture, and combining simulation analysis and real vehicle testing to verify the optimization effect. The results show that after optimization, the fault diagnosis accuracy of BMS has increased to 95.3%,the maximum battery temperature has decreased by 15.2 ℃ , the energy balancing efficiency has increased by 41.6%, the system communication bit error rate has decreased to below 10-6, and the operational reliability has increased by 23%.The research results have passed the ISO 26262 functional safety certification, which can provide theoretical and practical support for the technological upgrade of BMS and meet the conditions for industrial promotion.