Self-reconfigurable modular robots consist of many identical modules. By changing the connections among modules, the whole configuration of the robot can transform into arbitrary other configurations. In this paper, a hybrid self-reconfigurable modular robot is designed, which is composed of a master module and a slave module. Then, the docking process is analyzed with the geometric method. The docking states between two modules are presented. It is a complicated multi-peg-in-hole process.