The invention in particular relates to a precision machining method for a long and thin shaft of a cross-shaped wing bearing, which aims at solving the problem that precision is difficult to guarantee when a long and thin shaft of an existing cross-shaped wing bearing is processed. The precision machining method comprises the following steps: a, arranging a plurality of aluminum block fixtures composed of an aluminum block body on a working table of a machine tool; b, processing workpiece placing slots in the upper surfaces of the middle parts of two aluminum block fixtures; c, mounting on the workpiece placing slots by taking a work piece left wing end face as a positioning reference surface, and gluing at a seam by adopting 502 quick-dry super glue until a workpiece is fixed and then loosening the workpiece; d, after the positioning reference surface of the workpiece is checked to be qualified with a meter, starting to carry out finish machining; e, sequentially processing the upper wing end face, the left side, the right side, side surfaces of a left wing and a right wing and end faces of the left wing and the right wing above the aluminum block fixture, and meanwhile, measuring the thickness dimension of the workpiece; and f, unloading the workpiece and turning out the workpiece for 180 degrees, repeating the steps c, d and e until processing of the workpiece is completed, and unloading the workpiece. The precision machining method provided by the invention has the advantages that the machining quality precision degree is high, the production demand is met and the production efficiency is relatively high.