Ploughing technology has been applied in manufacturing micro grooves on the outer surface of copper tube. In order to study the formation of spiral grooves on the inner surface of tube, a FEM model operated on DEFORM is established. Two ploughing processes are simulated. At first, an initial groove is manufactured on the workpiece, and then a nearby groove, which will influence the initial groove's geometry, is manufactured with twelve feeds separately. The groove's geometries, including groove width, inclined angle and fin height, are detected. Geometry comparison between the two grooves show that different feed results in different groove shape. According to the geometry change tendency of grooves, the feed can be divided into three different intervals.