Considering the stability of a multi robot system with a specific leader mode, we derived a typical control method for the formation control based on consistency. Lyapunov stability theory and matrix theory were used for deriving the sufficient condition for the multi robot system formation to reach consistency, and the constrains for the system consistency protocol under the condition were obtained. The communication topological relation of the leader mode was set up randomly; the sufficient condition obtained was used for analyzing the convergence performance of the algorithm, and an algorithm satisfying the condition for this mode was presented. Digital simulation result verified the effectiveness of the proposed algorithm.