We study the multi-robot synchronization on a segment. The goal is for each robot to move along a subsegment of equal length in equal time interval with potential impacts. To achieve the synchronization, we propose a decentralized algorithm by designing impact laws, which do not depend on the positions of the robots, but on the time information. Specifically, “the time interval between two consecutive impacts” is exchanged when the robots meet. We also show how to apply the synchronization algorithm to a planar patrolling problem. Simulations and robot experimental results show the feasibility and robustness of our algorithm.