The invention discloses a low-incisura screw base and relates to the technical field of pedicle screws for orthopedic surgery. The low-incisura screw base is characterized in that a groove used for containing a limiting protrusion ring of a positioning compression ring is formed above clamping protrusions, and the inner diameter of the groove is larger than the diameter of the limiting protrusion ring of the positioning compression ring; the limiting protrusion ring which protrudes outwards and is matched with the clamping protrusion is arranged on a ring body and is located on the left side and right side of a bar containing groove, a rotation-preventing lug which protrudes outwards is arranged on the portion, located above or below the limiting protrusion rings, of the outer wall of the ring body, and a rotation-preventing clamping groove matched with the rotation-preventing lug is formed in each clamping protrusion. The installation method comprises the steps that when the limiting protrusion ring of the positioning compression ring is downwards installed in the groove between internal threads and the clamping protrusions in a screw base body from the position above an assembly hole in the mode that the limiting protrusion rings are opposite to two U-shaped grooves, the positioning compression rings are rotated to a position, opposite to the rotation-preventing lug and the rotation-preventing clamping groove, in the groove between the internal threads and the clamping protrusions on the inner wall of the screw base body, and then the positioning compression ring is punched downwards. The low-incisura screw base has the advantages that the diameter is small, and the incisura is low.