The invention discloses a spare part profile processing method. The profile line of a processed profile consists of an arc section and two straight line sections arranged on the same plane; and the two straight line sections are respectively connected with the left end point and the right end point of the arc section and are both tangent to the arc section. The method comprises the steps of establishing a plane rectangular coordinate system and adopting a numerical control machine to process the spare part profiles, wherein the plane rectangular coordinate system is established as follows: the circle center of the arc section is taken as an origin O of coordinates and the straight line on which the origin O of coordinates and the middle point M of the arc section are arranged is adopted as a longitudinal coordinate to establish the plane rectangular coordinate system; and the spare part profiles are processed by the numerical control machine as follows: 201: setting initial parameters; 202: calculating the coordinate values of each end point of processed profile lines; and 203: machining. The spare part profile processing method has the advantages of reasonable design, simple processing steps, convenient realization and strong commonality as well as low error rate. Moreover, the practical problems like longer time spent on calculating coordinate points and programming corresponding software programs and high error rates existed in the profile processing process consisting of double straight lines and an arc in a tangent way.