The invention discloses a structure and manufacturing process of a low-cost carbon fiber composite material empty rail car body, which belongs to the technical field of application of composite materials on rail vehicles, and includes car body side walls, and both ends of the car body side walls are assembled The end wall is connected, the inner top surface and the inner bottom surface of the side wall of the car body are respectively assembled and connected with a top frame and the bottom frame, and the outer top surface of the side wall of the car body is assembled and connected with a ceiling, and bogie mounting holes are opened on the ceiling; The side wall and the end wall of the car body all include a stiffener skeleton, an inner skin and an outer skin, and the grid of the stiffener skeleton is filled with sandwich foam blocks; the roof includes a sandwich laminate, an upper skin and a lower skin skin; the top frame, the bottom frame, the rib skeleton, the inner skin, the outer skin, the upper skin and the lower skin are all integrally molded by carbon fiber composite materials; the inside of the rib skeleton is filled with sandwich foam, The purpose of meeting the function and structure of the bearing mode of the suspended car body is achieved under the premise of light weight of the car body.