Screw cooling system of single-screw extruder comprises a hollow screw with a sequentially arranged shank, a screw-tapped section and a tip. The screw-tapped section contains sequentially arranged feeding, melting and homogenizing zones, as well as a pipe placed in the screw cavity on the shank side for supplying coolant to the screw cavity. At least one through hole is made in the wall of the coolant supply pipe in the area of transition from the feeding zone to the melting zone of the screw