For describing the topology information in the reconfiguration process of self-reconfigurable robot, an UBot self-reconfigurable robot topology description method based on incidence matrix is proposed. At first, a joint state table during the reconfiguration process is built up based on the analysis of the module motion characteristic of UBot self-reconfigurable robot system; and then a binary number representation is developed by analyzing the linkage and position relation that may exist among modules; finally,taking worm configuration as example,the corresponding topology description matrix is obtained,which can describe not only the information of module address,module connection status and position relation,but also the joint angle status information of each module exactly. This topology description method is helpful to the research of configuration matching and reconfiguration algorithm of reconfigurable robot.