For prefill valve on the ceramic brick machine produce larger vibration in the process of rapid downward, its speediness and stability should be analyzed. The different flow fields with the 10% gas volume rate and the 50% gas volume rate under the 02 MPa pressure in prefill valve were analyzed, as well as the 20% gas volume rate under the 015 MPa pressure. Then the flow fields were compared with the theoretical calculation to validate the correctness of the 3D fluid simulation model. It provides reference for the design and structure optimization of the prefill valve on the basis of the analysis to the flow field distribution of the optimized prefill valve.