The venturi tube in the automotive desorption system is a device that utilizes fluid dynamics principles to achieve gas mixing and transmission. Optimizing the structural parameters is particularly crucial for improving vehicle emission performance. By employing the advanced numerical simulation technology, the fluid dynamic characteristics within the vehicle venturi tube was analyzed and the influence mechanisms of key structural parameters on flow characteristics and operational efficiency were explored. These parameters included mixing tube length, the ratio of drive nozzle diameter to mixing tube diameter (d_mr/d_td), thrust gap width, diffuser diameter and diffusion angle. The results indicate that all parameters significantly influence the suction performance and operational efficiency of the venturi tube. Detailed influence patterns for each parameter across different driving pressure ranges are elaborated, along with proposed optimization strategies.