Traditional robots are developed to achieve specific goals or functions. They are mostly tracked, footed, rod-type and other structures. They are suitable for structured scenes such as flat ground, slopes, walls, etc. They are obviously restricted by the terrain. At the same time, the functions are relatively simple. After the whole machine is designed and manufactured, the functions cannot be easily expanded. Compared with traditional robots, modular robots have the advantages of diversity, reliability and scalability, and are more suitable for unstructured scenes. This paper summarizes the common chain-type, crystal-type and hybrid modular robots from the perspective of structural morphology. On this basis, this paper proposes a spherical robot unit as the base unit of the modular robot and completes the body construction of the base unit through structural and circuit design. The modified D-H parameter method and Newtoon-Euler method are used to complete the kinematic and dynamic modeling respectively, and the motion simulation of “BaseUnit” is realized in the Simscape Multibody simulation environment, which preliminarily verifies the feasibility of BaseUnit to realize the self-reconfigurable modular robot system.