Abstract: In the real environment of multi-robot formation task, it is inevitable to encounter the dynamic formation problem of formation transformation. To improve the dynamic cooperative obstacle avoidance ability of multi-robot formation in unstructured environment, taking the multi-robot system of large-load-ratio six-legged robot as an example, an obstacle avoidance strategy of dynamic formation transformation for the cluster consensus of multi-leader robots is proposed by using the leader-follower formation idea of the trajectory tracking of nonholonomic constrained mobile robots. Based on the mathematical foundation of algebraic graph theory, the communication topology and topology analysis matrixes of multiple large-load-ratio six-legged robots are designed. The global dynamic relationship and consistency mathematical model of the multi-leader cluster consensus formation system are established. The obstacle avoidance strategy of dynamic formation transformation is proposed on the cluster consensus formation control of multi-leader robots. The simulation experiments are carried out based on MATLAB software. The simulation results show that the virtual leader robot issues the control commands to make the multi-robot system complete the formation transformation and smoothly pass through the obstacle environment. Then, the effectiveness and generalization ability of the obstacle avoidance control strategy are verified for the multi-robot dynamic cooperative formation. The proposed obstacle avoidance control strategy of multi-robot dynamic cooperative formation for the large-load-ratio six-legged robot is helpful to improve the terrain passing ability of multi-robot system in unstructured environment.