Abstract: In order to improve the fuel economy of the engine, the influence of tumble ratio on fuel economy is verified by partial load test; the accuracy of three-dimensional steady calculation model and the relationship between flow coefficient and tumble ratio is verified by ports steady test. The geometric parameters of affecting ports flow characteristics are analyzed based on CFD(Computation Fluid Dynamics), fitting out an approximate model with the Optimal Latin hypercube sampling and response surface method (RSM). Optimizing the tilt Angle and throat Angle via the Elitist Nondominated Sorting Genetic Algorithm (NSGA-Ⅱ), it confirms the optimized design scheme by comparing the flow coefficient and tumble ratio. The result shows that the optimized inlet model can improve the tumble ratio on the premise that the flow coefficient is constant, which can eventually get the optimal design result of improving the tumble ratio.