The invention discloses a large self-balancing type safe and labor-saving cover plate device which is used for being arranged at a lifting opening of floor slabs, and a framework is arranged around the lifting opening. The large self-balancing type safe and labor-saving cover plate device comprises a pair of guide rails, multiple cover plates and a lifting device, wherein the guide rails are respectively arranged on two opposite sides of the lifting opening, one end of each of the pair of guide rails is connected with the framework in a pivoted mode, the multiple cover plates are movably supported on the pair of guide rails, and the cover plates have an unfolded state and a folded state. The lifting device is used for lifting and descending the other end of each of the pair of guide rails so that the multiple cover plates are enabled to be switched between the unfolded state and the folded state. According to the large self-balancing type safe and labor-saving cover plate device, through the change of the rotation angles of the guide rails relative to the framework, a purpose of adjusting the gravity centers of the cover plates is achieved, and therefore the heavy cover plates can be opened and closed through utilization of self weights of the cover plates without the need of any additional auxiliary devices, the manufacturing cost is lowered, the problem that long cover plates cannot be manufactured on the principle that the folded cover plates only rely on counterweight is solved, and the operation process is enabled to be simpler and more convenient.