A conjugate-reflection-based time-synchronization measurement method is proposed for target points of a high power laser facility. First, two parallel reflectors with equal distances from the target point are placed on both sides of the target point, and simultaneously two high-speed photodiodes are placed on the conjugate image point of the target point. Second, two laser beams from the up and down hemispheres in the target chamber are reflected to the two photodiodes placed on the conjugate image point of the target point, and the time interval between two output signals from the two photodiodes is just the time-synchronization difference between the optical paths to be measured. The proposed measurement technology possesses nice characteristics of simple operation, high test efficiency, which has been successfully applied in the time-synchronization measurement of multiple laser beams in high-power laser facilities.