The invention relates to the technical field of plastic bag processing equipment, and discloses a perforating machine for plastic bags. The perforating machine for the plastic bags comprises a motor and a perforating table; a releasing roller and a coiling roller are arranged at the two ends of the perforating table respectively; a perforating groove is formed in the middle of the perforating table; an eccentric wheel is arranged on the releasing roller; a first push rod is hinged on the eccentric wheel; an elastic piece is arranged at the bottom of the perforating groove; inflatable cushion blocks are arranged at the two ends of the elastic piece; a support is arranged on the perforating table; an air cylinder is arranged at the upper end of the support; an inflatable bag is connected to the lower end of the air cylinder; an air pipe is connected on the inflatable bag; the other end of the air pipe communicates with the two air inflatable cushion blocks at the same time; an air pump is arranged on the air pipe; the outside of the inflatable bag is wrapped with a spherical cooling bag; perforating knives are arranged at the lower end of the cooling bag, and the cooling bag is internally provided with a cooling liquid and is connected with a cooling groove, and the cooling groove is connected with a cooling fan; a sliding channel is arranged on the cooling fan; a piston is arranged in the sliding channel; a second push rod is hinged to the piston; and the other end of the second push rod is hinged to the first push rod. According to the perforating machine for the plastic bags, the knife distance of the perforating knives can be adjusted.