The formation control of multi-robot systems in complex environments is a challenging problem, which needs to handle velocity estimation and obstacle avoidance problems. However, few researches considered these problems simultaneously in the literature. In this paper, a leader-follower hybrid formation control design for multi-robot system is proposed, which simultaneously solves leader-follower formation control problem, velocity estimation problem, and obstacle avoidance problem. First, based on the leader-follower architecture, formation control law is designed. Second, considering the difficulty of obtaining the whole accurate velocity information, a velocity estimator of the leader is designed, and the Lyapunov function is used to analyze the stability of the multi-robot system. In addition, the artificial potential field (APF) method is adopted to avoid obstacles in complex environments. Finally, an experimental platform of the multi-robot system is constructed, and simulation and experimental results verify the effectiveness performance of the leader-follower hybrid formation control design for the multi-robot system.