A rotating cylinder includes and a main body, a piston head, a piston rod and a guide assembly. The piston head slidably is received within the main body. The piston rod partially received within the main body, the piston head is fixed to the piston head, the piston rod defines one or more guiding groove adjacent to the piston head, the guiding groove includes a straight portion, a first helix portion and a second helix portion, the straight portion extends axially toward the piston head, the first helix portion curvedly extends away from the straight portion toward the piston head, the second helix portion curvedly extends from an end of the first helix portion toward a direction away from the piston head and the straight portion. The guide assembly is mounted on the main body and includes one or more guiding member slidably engaged with the guiding groove.