The invention belongs to field of solar device, particularly relates to a method for preparing continuously a selective absorbing composite film of collector sheet for solar light/thermal conversion in large scale through utilizing magnetron sputtering technology. The continuous preparation method of a selective solar absorbing film comprises pretreatment of base material and vacuum plating of composite film, the process of plating a plurality of layers of composite films on metal thin-plate coiled material is conducted continuously; for the metal thin-plate coiled material, during the process of winding and unwinding of the winding device and the unwinding device, the plating of multi-layer composite coating for the coiled material passing through process rooms arranged between the winding device and the unwinding device is conducted by the process room, an isolating device isolates a treatment room from the plurality of process rooms; when the continuous metal thin-plate coiled materials pass through the pretreatment room and the plurality of process rooms continuously, the invention can provide a process method for generating continuously a solar absorbing film for a long period of time through utilizing magnetron sputtering technology, and has advantages of high production efficiency and stable product quality.