Research has been conducted on a piston type positive displacement pump, which is a system for the direct pressurization of hydrogen, used as a filling technology in the automobile hydrogen stations for the delivery of pressurized hydrogen gas to fuel cell powered vehicles. New design of the inlet valve had been investigated in order to improve the suction performance of liquid hydrogen in the high pressure pump. Newly designed valve consists of three parts, such as main valve, assistant valve and additional inlet piping. There is hydrogen gas caused by the leaking from the seals of the main valve or heat leak at the suction potion of the cylinder. This condition is not good for the suction performance. But combinations of these parts work well to improve the suction performance even if there is hydrogen gas. It had been proved that suction performance of 40MPa class high pressure pump was improved in the experiment of pressurization of liquid hydrogen with this new designed valve compared with conventional type valve.