A socket rail pedicle screw includes a fixator, a spherical head screw pivotally disposed at a bottom of the fixator and a retention screw cap. The fixator has a circular sidewall and a though hole. A pair of U-shaped grooves is defined on a top portion of the circular sidewall and a pair of locating steps is internally extended from an inner wall of a bottom portion of the circular sidewall and below the U-shaped grooves. The spherical head screw includes a bolt and a pair of diametrically faced socket rails. Each socket rail is constructed by a second top wall and a corresponding second sidewall extended from the second top wall to the bottom of the head. The second top wall is vertically pressed against the first top wall, both of the first and second sidewalls are arced, and a gap is defined between the first and second sidewall.