Considering that the capacitance value of thyristor controlled series capacitor (TCSC) can be adjusted quickly in capacitive mode, and that accumulated energy can be released in bypass mode. A control strategy is presented for improvement of dynamic stability in multi-machine power system. TCSC inputs maximum capacitive compensation in a appropriate time when equivalent generator of multi-machine power system accelerates relative to center of inertia (COI) after a fault, yet TCSC operates in bypass temporarily mode for deceleration. TCSC adopts conventional dynamic control during other time. By IEEE4 machine 10 nodes system simulation experiment, the effectiveness of the controller is verified.