Liquid piston hydrogen compressors (LPHCs) are promising used in hydrogen refueling stations. Piston braking is crucial to LPHCs since the solid piston works under a high stroke frequency, which may result in piston collision. The on-off valve in the previous studies requires complicated control program to ensure the piston positions at dead centers. In this paper, a novel LPHC with a double buffer structure and an improved hydraulic driving system are proposed. A simulation involving the flow through the buffer aperture confirms the braking effect of the proposed design. Some parameters affecting piston braking are studied. A light piston can produce a lower velocity pulsation and lower peak pressure in the buffer chamber. The minimal piston displacement decreases with an increase in the bottom throttle diameter, while the maximal piston displacement increases with an increase in the top throttle diameter. The results also show that the slight pulsation of the piston velocity is attributed to the spool insertion, the piston reverse motion, and the opening of valves. This study can provide a technical reference for the optimization of LPHCs. Display omitted •A liquid piston compressor is proposed for hydrogen refueling stations.•Double buffer structure facilitates piston braking and avoids collision.•Reducing piston mass declines the pulsation amplitude of piston velocity.•Adjusting throttle diameters can change the positions of dead centers.