The dynamic coefficients are the essential parameters, which could be used to determine the critical rotational speed, an unbalance response and the stability analysis. A plural mathematic model of the coefficients calculation is developed by using the numerical perturbation method. A spring model is applied to get the foil deformation. The dynamic coefficients of the gas foil bearings are obtained through the application of the finite difference method and the finite element method. The results show that the dynamic coefficients are closely related to the journal eccentricity and whirl ratio. With the results compared to the published data, the model is proved to be accurate. And the coefficients could be used as a reference for the design of a gas foil bearing.