The invention discloses a composite steel bar FRP stirrup and a preparation method thereof. The composite steel bar FRP stirrup comprises an FRP wrapping layer, a steel bar, ribs and fiber cloth, wherein the FRP wrapping layer is arranged outside the steel bar; the ribs are arranged outside the FRP wrapping layer; the fiber cloth wraps the steel bar at the bending section of the stirrup; the FRP wrapping layer is formed by curing continuous fibers and resin at high temperature; the steel bar can be a plain round steel bar or a ribbed steel bar; and the steel bar is positioned at the center ofthe section of the composite steel bar FRP stirrup. The composite steel bar FRP stirrup and the preparation method thereof have the advantages of high engineering modulus and shear resistance, can meet the requirements of civil engineering structures, and are suitable for large-scale popularization.