Abstract: This application provides a vehicle DC voltage conversion circuit, including a high voltage battery connected in sequence, a primary-side-bridge module, a resonant module, a transformer module and a secondary-side-output module, wherein the secondary-side-output module includes a first voltage unit outputting a first voltage and a second voltage unit outputting a second voltage. The secondary side winding of the transformer is connected with the first voltage unit and the second voltage unit; The circuit also includes a driver module connected with the original side bridge module. The vehicle DC voltage conversion circuit provided in this application can not only output the first voltage, but also output the second voltage at the same time. It has the advantages of small size, high efficiency, low cost and industrialization, and can be widely used in the vehicle 48 V electrical load, such as 48 V vehicle electric heating system, 48 V vehicle cooling fan, and so on.