Abstract: To model the 3D surface of a cylinder with the data from the straightness measurement, the straightnesses of a number of generatrices were measured with the method of EST, and by means of the data of the beginning and end sections, the least square mean axis was calculated to represent the actual axis of the workpiece. By rotating the abscissas, all data of straightness were transformed into a unified 3D coordinaties whose z axis is the actual axis. Then the 3D model of the surface was constructed. The computer simulation has proved that the construction by rotating the abscissas can effectively eliminate the distortion of the constructed surface.