The invention discloses a gasoline engine RCV valve positioning tool. The tool comprises a support frame, and a positioning module arranged at the upper part of the support frame for positioning workpieces; the positioning module includes a left stopper, a right stopper, a left positioning block and a right positioning block; the left positioning block and the right positioning block are respectively fixed on two sides of the upper part of the support frame; the left stopper is supported on the left positioning block; the right stopper is supported on the right positioning block; extension parts for stopping the workpieces are respectively arranged on the opposite sides of the left stopper and the right stopper; space for inserting in the workpieces is left between the inner side surface of each extension part and the outer surface of the support frame; and slot positioning space for positioning the workpieces is formed among the left stopper, the left positioning block, the extension part of the left stopper, the right stopper, the right positioning block, the extension part of the right stopper and the support frame. The gasoline engine RCV valve positioning tool is simple in structure and convenient to operate, and can realize quick positioning of RCV valves.