Abstract: A modular self-reconfigurable robot based on universal joint is presented,namely UBot.The UBot module is of compact structure,high strength and flexible movement,and is capable of performing efficient locomotion,self-reconfiguration and manipulation tasks.This robot consists of several standard modules.Each module is of cubic structure based on universal joint,and has four connecting surfaces that can connect to or disconnect from adjacent modules.A hook-type connecting mechanism is designed,which can connect to or disconnect from adjacent modules quickly and reliably. This mechanism can self-lock after connection,and is of energy-saving.The electrical system of module is designed.Finally, through the experiments of the connecting mechanism and UBot locomotion,the reliability and flexibility of UBot system are proved.