The invention discloses a cast-in-place pile head breaking method. The cast-in-place pile head breaking method comprises the following steps: a concrete isolation layer and a pile head lifting piece are installed when a reinforcement cage is manufactured; the reinforcement cage is hoisted in place, and pile body concrete is poured; a PVC pipe is pulled out after the concrete is initially set for 30-60 minutes; an external foundation pit of a mounting body is excavated; the pile head is separated and lifted; and a flexible sleeve and a two-claw metal anchor are recovered. The method has the advantages of convenience and fast; the pile head breaking process can effectively avoid damage and deformation of main reinforcements; the PVC pipe, the flexible hose and the lifting device can be repeatedly used; the pile head breaking cost is effectively reduced; and the method is suitable for breaking various types of cast-in-place pile heads.