The invention discloses a fixture for machining a curved grove on the cylindrical surface of a perforated workpiece. The fixture comprises a rotating shaft and a first pull bar, wherein the rotating shaft and the first pull bar are mutually connected to the inside of a base. The rotating shaft is capable of rotating relative to the first pull bar. A first worm wheel is horizontally sleeved on the rotating shaft. A rotatable top shaft is vertically disposed at the top of the base. A second worm wheel is vertically sleeved on the rotating shaft. The first worm wheel and the second worm wheel mesh with each other. The upper surface of the second worm wheel is provided with a radial guide groove, and a guide bar with bottom slidably connected into the guide groove is vertically disposed on the guide groove. The tail of the first pull bar is bent up to be level to the top of the guide bar, and a second pull bar connected with the tail of the first pull bar and the top of the guide bar is disposed at the tail of the first pull bar. When rotating, the first worm wheel can drive the second worm wheel to rotate to drive the guide bar to slide in the guide groove so that the first pull bar is pulled by the second pull bar to axially advance and retract to make a curved groove on the cylindrical surface of the workpiece. Therefore, machining cost is low, and machining efficiency is high.