The invention discloses a method for efficiently decomposing and recycling valuable metal in copper slag. According to the method, after the copper slag and cryolite are mixed and ball-milled, the mixture is arranged in an air atmosphere for calcination; calcination products are crushed and undergo magnetic separation, and then magnetite is obtained. By the adoption of the method for efficiently decomposing and recycling the valuable metal in the copper slag, iron resources incapable of being reused in the copper slag can be directionally regulated and controlled to be efficiently converted into the magnetite under mild conditions, reduction and reclamation of the copper slag are achieved, the copper slag tail end single-pass treatment problem, the national high-grade iron ore resource starvation problem, and the environmental pollution problem are solved, and a green sustainable development road is opened up for treatment of the copper slag.