For the purpose of achieving the lightweight of automobiles, the contact friction process between the taper leaves was deduced with equations such as the deformation equations and stress equations, which were based on the taper leaf spring of the mini-car. Based on the genetic algorithms, a mathematical optimal model of the two taper leaves spring with variable stiffness was built to simulate in the software of MATLAB. A FEM model of the leaf spring was also built to check the mathematical model by using the ANSYS. In conclusion, it has been found that the grams of the material can be reduced by 31.6% without affecting the performances of the requirements, by comparing the difference between the optimal test results and non-optimal test results.