The invention discloses an underpan assembly. The underpan assembly comprises a bearing frame and at least four walking units, wherein the walking units are arranged on the bearing frame; each of the walking units comprises a support leg, a wheel support, a steering motor and a walking wheel, wherein the support leg is connected to the bearing frame, the wheel support is arranged in a rotatable mode, the steering motor is arranged on the support leg and used for generating power enabling the wheel support to rotate, and the walking wheel is arranged on the wheel support. The underpan assembly is simple in structure, high in reliability, easy to machine and manufacture, convenient to steer, and flexible in steering, has good rideability, is not only applied to free moving of the robot, but also applied to free moving of any object which is not convenient to move and greatly facilities moving of machines which are heavy and not easy to move.