The invention discloses a combined anti-loosening fastener, and relates to the technical field of fasteners. The fastener comprises a bolt, a nut and an anti-loosening washer; the upper end surface of the anti-loosening washer is coaxially and fixedly connected with a ratchet wheel, the outer diameter of the ratchet wheel is smaller than that of the anti-loosening washer, radial wedge-shaped teeth are annularly arranged on the lower end surface of the anti-loosening washer, the orientation direction of the side end surfaces of the wedge-shaped teeth is consistent with the unscrewing direction of the nut, the bottom end of the nut is fixedly connected with a female cover, the female cover can cover the ratchet wheel, the bottom end of the female cover can be pressed on the upper end surface of the anti-loosening washer, a plurality of pawls matched with the ratchet wheel are arranged on the side wall of the female cover, and one end of the rod part of the bolt can sequentially penetrate through a workpiece, the anti-loosening washer, the ratchet wheel, the female cover and the nut to be connected with the workpiece in a fastened mode. When being used for fixing an object, the anti-loosening fastener can effectively prevent loosening, and is convenient to assemble and relatively low in machining difficulty.