is particularly important to establish the deepsea simulation system in the laboratory for research work when considering the particularity of deepsea environment and the difficulty of the observation and research on the spot. Aiming at existing deepsea pressure simulator, the change of the geometry size of the pressure cylinder after the pressure arrived 5 MPa was analyzed. According to the relevant calculation formula, the airtight vessel iterative relationship between liquid volume change and pressure variation was deduced, then the relationship diagrams between the large and small piston feed rate and the changes of pressure were plotted through the calculation software MATLAB, and the relationship between the feed rate and the changes of pressure was approximate linear, measuring pressure through the displacement sensor of high precision was analyzed and higher precision could be gotten than the standard pressure sensor. Then small pressure fluctuation can be calibrated accurately by displacement sensor.