This paper presents a geometrical error analysis of wheel curve generation method for micro aspheric surface machining using parallel grinding method. In aspheric grinding, wheel wear in process is crucial parameter for profile error of the ground surface. To decrease wheel wear, parallel grinding method is adopted. Wheel and work piece (Tungsten carbide) contact point changes during machining process. In truing process of the wheel, radius is determined by the angle and distance between wheel and truer. Wheel radius error is predominantly affected by vertical deviation between the wheel rotation center and the truer center. Simulation for vertical error and wheel radius error shows same tendency that expected by geometrical analysis. Experimental results show that the analysis of curve generation method matches with simulations and wheel radius errors.