The invention relates to the technical field of classification treatment of plastic bottle materials, in particular to an automatic bottle cap separation machine for plastic bottles. The automatic bottle cap separation machine comprises a rack, a machine box, a direct-current drive motor, a driving intermittent gear, a driven intermittent gear, a center transmission shaft, a rotary disc, rotary arms, locating front concave plates, locating rear concave plates, springs, locking devices, a cam, a variable-speed motor, a spiral cutter, a claw-shaped bent hook, an arc-shaped sliding groove, an arc-shaped baffle, an arc-shaped pressing plate and the like. The combination manner of manual feeding and mechanical automatic machining is adopted for production, so that locating clamping, cutting, bottle cap and bottle mark separation, automatic recycling and a series of actions on the plastic bottles can be completed through the mechanical device. The automatic bottle cap separation machine is mainly used for regions with large population density and mobility such as shopping malls, supermarkets and schools; consumed empty bottles are directly put into the machine, the machine is started and conducts automatic machining, the machined bottle marks, bottle caps and bottle bodies automatically fall into corresponding collection boxes on the lower portion, no specially-assigned person is needed for operation, and manual handling is conducted after the collection boxes are full.