The modeling of a modular robot system is complex due to its capability of changing and forming countless robot configurations with a set of modules. The greater the number of modules added to the structure, more complicated is the robot and its modeling. A methodology to represent modular robot configurations as a fixed shape robot is presented. The equivalent model is obtained through the characterization of the module, graph theory and geometric modeling of robots. After the transformation, the resulting kinematic and dynamic parameters are similar to the traditional model of a single configuration robot. Once the equivalent model is obtained, it can be used within different robot applications.