This paper presents a 48V electrical system based on tail gas thermoelectric power generation, which mainly includes a thermoelectric power generation device, a 48V lithium battery pack, a 24V lead-acid battery, current and voltage type double DC/DC, etc. The energy flow of the traditional and new 48V electrical system under different states of ignition and cruising is analyzed. By comparing the fuel consumption rate and the SOC value of the 24V lead-acid battery, a logic-threshold based control strategy is designed to achieve the optimal energy control. The modeling and constraining conditions of the 48V electrical system for the vehicle have been completed, and the corresponding simulations have been performed using the ADVISOR software. The experimental results show that the maximum power of thermoelectric generation can reach 1500 W, the average efficiency of thermoelectric generation is about 4.5%, and the corresponding fuel saving rate can reach 1.45%.