Abstract: A new method for establishing aeroengine's State Variable Model (SVM)-fitting method is proposed.The SVMs of small perturbation about steady operating points of an engine are established by fitting nonlinear dynamic simulation data of its component-level models at the points.Then the SVMs of small perturbation about steady points at ground and in flight and also the SVM of large perturbation of ground acceleration for a turbofan engine are established by this method.Dynamic simulation results show that the SVMs established by fitting method have much higher accuracy than the SVMs established by the method of bias derivative.