An in-die tapping machine transmission screw rod torsion overload protection device comprises a main shaft, a gear arranged on the main shaft body in a sleeved mode and a friction plate, wherein the friction plate comprises a small-diameter part and a large-diameter part, concentric circles on the upper end face of the small-diameter part are provided with a plurality of first steel ball grooves at equal-interval radians, first steel balls are contained in the first steel ball grooves, and the first steel balls are matched with a first rolling groove in the lower end face of a journal of the main shaft; a plurality of through holes are evenly formed in the radial direction of the large-diameter part, a set screw is screwed into openings in the outer sides of the through holes for sealing, the set screw makes contact with a steel ball sleeve through a compression spring, second steel balls are contained in the steel ball sleeve, and the second steel balls are matched with second steel ball grooves evenly distributed in the outer circumference of the main shaft body. The in-die tapping machine transmission screw rod torsion overload protection device is reasonable in structure and ingenious in concept, a transmission screw rod is protected, a transmission cup is not damaged when power transmission is blocked because workpieces are abnormally machined or there is transmission resistance in a machine, and a feasible new industrial technology is provided.