The engine air intake system is considered as a subsystem that restricts the main performance of the vehicle power system, and has been regarded as one of the keys to design optimization in the improvement of vehicle power performance. Based on this, the research has carried out the analysis of the intake effect of the relevant dimensional parameters of the intake manifold in the racing environment. On the premise of the existing engine entities, the research first constructs a complete engine digital analysis model, obtains the reference size parameters of theoretical analysis, and then couples other engine performance index parameters, so that the accuracy of the simulation results can be verified by the engine bench tests. Finally, under the application of single factor variable control method, the specific relationship between geometric parameters such as intake manifold length and inner diameter on engine design performance has been analyzed quantitatively. The results have shown that the results based on digital model analysis have high mechanical fidelity, which can be used as a reference for improving engine performance in subsequent racing and passenger car design.