In view of the limitations that the tuning of shock absorber costs an engineer who depends on experience much time and strength, the thought of reverse solution was introduced, and then the forward modeling idea of shock absorber and reverse solution of key parameters were studied. Firstly, according to the thought of combining finite element analysis and least squares, a characteristic forward model based on large deflection was established. Furthermore, the obtained analysis results clearly identify some significant parameters which have a large impact on the process of the tuning of shock absorber. Based on the damping characteristic curve of shock absorber, the reverse model was established, which takes the errors between the simulation and test data as the objective function and takes the key parameters as the unknown parameters. Finally, some parameters of throttle-slices which are important to valve deflection were identified by using GA. The simulation results of parametric model after reversing agree well with the test data. This study provides a theoretical foundation for parameter optimization of shock absorber, in the case of the unknown important parameters of shock absorber. Meanwhile, this method provides a basis for the tuning of damper performance.