The main cause of crack initiation of steam turbine rotors in "S" power station is the short startup time at high temperature. The convection heat transfer coefficients at the flange of labyrinth on the left of the control stage varies rapidly during the startup. The equivalent stress increases higher than the yield stress. There must be plastic strain, thus, the low-cycle fatigue occurs. A new reasonable startup method which can ensure the safe of the operation of the rotor and give economic benefit is suggested using quality engineering method.