Abstract: Based on the existing Venturi nozzle fluid supply system, an axisymmetric two-dimension computation model was presented. Flow field characteristics of Venturi nozzle under different back pressures were calculated using computational fluid dynamic methods. The numerical simulations demonstrate that, shock waves in the pipeline go through three states owing to back pressure’s increasing: oblique shock wave in straight circular pipeline, pseudo-normal shock wave in endocone adapter connector, and normal shock wave in Venturi nozzle. During the design of Venturi nozzle flowmeter, normal shock waves must be restricted beside the throat of Venturi nozzle or within a short distance downstream from the throat, which offers the advantages of low total pressure loss and stable flow field. Wall-dril