Pressure reducing and control is the key technology in hydrogen transmission for fuel cell cars. A double step system with two direct reducing valves had been provided in this paper. These two valves depressurize the tank hydrogen pressure from 35MPa or 70MPa to 5MPa at first, then to 0.16MPa, adapting the fuel cell demands. The valves static analysis show the flow rate and pressure characteristics are rigid. The dynamic simulation display the valves quick response and pressure control accuracy are satisfied fuel cell working condition. The analogue experiments verify the system reducing performance and the double step reducing system is applicable to fuel cell cars hydrogen transmission.