The measurement method of standard helix surface in the national standard was summarized and the common properties and methods of common screw and screw bar in geometric error measurement were gained. Based on the envelope principle of complex surface in differential geometry theory, the surface equation of a workpiece was studied with the method of coordinate transformation and relative motion. The general formulas were presented for the generalized helix surfaces in the condition which the curve equations of generatrixs have been obtained. Through the analysis of measurement factors in generalized helix surface, the measurement method for the abnormity helix surface has been got. Combined with the general formulas, a unified theory of measurement method for generalized helix surface was presented. This theory will provide the theoretical base of the online measurement of generalized helix surface.