A self-optimized method was employed to establish the state space model(SVM)

that is

A

B

C

D matrices were given arbitrarily

then small perturbation response between nonlinear model and SVM was compared to seek the exact A

B

C

D matrices directly.This method aims at inosculating the response between nonlinear model and SVM

so high precision could be guaranteed.This method is not limited by the order of model.One small perturbation SVM of a certain turboshaft engine model has been established by this method

and the simulation result between SVM and nonlinear model was also compared

proving the validity and accuracy.Also

the SVM could be applied to fault diagnosis and control system design for aero engines.