The output laser pulse cannot sustain a flat-top temporal profile owing to the time domain distortion caused by gain saturation effect in laser amplifiers during the transmission and the amplification of high energy pump laser pulse. Therefore, the pump laser pulse needs to be pre-shaped to compensate the gain saturation in the amplifier. A temporal shaping technology based on optical-optical synchronization amplification is proposed to compensate the time domain distortion caused by gain saturation. The proposed technology is based on the conventional amplification model, and it is not restricted to the width of laser pulse. The proposed technology is simple to operate and costs low. Theoretical simulation results indicate that the effective temporal shaping for the input pulse of laser system can be achieved and the gain saturation can be compensated by the proposed technology, and the output pulse with flat-top shape in time domain can be obtained.