Abstract: A mathematical modeling and digital simulation technique of gas turbines based upon the component characteristics is presented. The computer program of the engine model posses three main functions: to calculate the steady state characteristics of the engine from idle to maximum power under different intake ambient conditions; to calculate the coefficient matrices (or dynamical parameters) of the linear dynamical model under the corresponding calculating points; and to simulate the transient responses of the engine under small perturbations or large perturbations acceleration from idle to maximum power or deceleration from maximum to idle power digitally. However, a steady and dynamical simulator of gas turbine engine is presented for predicating the performance, estimating the affecting factors of the engine and selecting the appropriate parameters of the engine and its control system in design or actual operation.