In order to correctly understand the theory of tooth surface envelope forming and the theory of the finger-shaped milling cutter processing for equal base circle bevel gear， and to realize its correct machining, based on the principle of equal base circle bevel gear, according to the cutting coordinate system of fingermilling cutter and tooth surface equation, the calculation method of indexing angle for the conversion between the concave and convex during the machining is studied. The single tooth surface model of bevel gear was accomplished, and the concave and convex model was built at the same time. The generation process of tooth surface and its space geometry relation for concave and convex were validated. By means of coordinate transformation, threedimensional (3D) modeling in the same coordinate system for concave and convex of equal base circle bevel gear and finger-milling cutter was completed under machining condition. The correct space geometry position relationship between the cutter and the tooth surface is verified, which provides an effective means for previous validation on the machining of equal base circle tooth surface.