The invention relates to method for processing oil grooves in inner bores of a copper bearing bush through a common lathe, which comprises the following steps: (1) fixing the copper bearing bush in a fixture body, and fixing the fixture body on a tool rest of the lathe; (2) inserting one end of an auxiliary positioning support tool into a Morse taper hole of a tail rack sleeve of the lathe, and processing a cutter arbor hole at the other end thereof; (3) passing a cutter arbor fixed with a blade through the copper bearing bush, clamping one end thereof on a lathe head, and extending the other end thereof into the cutter arbor hole; (4) starting the lathe to rotate the cutter arbor, moving the tool rest of the lathe, setting the starting position and depth of an oil groove, and flexibly processing the oil groove in the length; and (5) after the first oil groove is finished, retreating a tool bit, stopping the lathe, loosening a fastening piece, rotating the copper bearing bush 180 degrees in the fixture body, fixing the copper bearing bush, and repeating the step (4) to process the second oil groove. The method can be used for processing the oil grooves in the inner bores of the copper bearing bush through the lathe, the cutting force is small, high processing quality and production efficiency can be realized, and a requirement of mass production is met.