Abstract: In order to study the influences of aero-engine power extraction on starter power selection, torque balanced method is put forward to solve the problem of starter power selection and a mathematical model is established based on engine research experience and rotor torque balanced equation. Rotating speed rising rate of engine and power requirement of starter are computed in different power extraction quantity and initial rotating speed with the model based on computing platform of a certain turbofan engine and air turbine starter. The results show that rotating speed rising rate descends and starting time increases with power extraction quantity increasing and power extraction initial rotating speed decreasing, and vice versa. When the power extraction quantity increases and the initial rotating speed decreases, the maximum output power of starter should be raised in order to maintain the rotating speed rising rate.