A novel approach for real-time detection of lithium-ion battery thermal runaway has been proposed to enable the monitoring of thermal runaway states during storage, transportation, and use, and to prevent safety hazards such as fire and explosion. This approach uses the fusion of high-precision, high-sensitivity photoelectric and electrochemical detection techniques based on the dual-wavelength principle. To analyze the thermal runaway mechanism of lithium-ion batteries, four important gas parameters -CO, EX, H 2 , and CO 2were obtained to indicate the thermal runaway state, and the characterization of these parameters under different thermal runaway states of lithium-ion batteries was studied. A real-time detection system is designed and validated through experiments involving overcharging, over-discharging, and puncturing of lithium-ion batteries. This method is suitable for the real-time detection of thermal runaway in lithiumion battery products and can also provide a basis for evaluating the life and reliability of lithium-ion batteries.