A reliable algorithm was developed for the analysis of the machined aspheric surfaces with the stylus instrument. The research has been done as a prior step, with the intent to evaluate the uncertainties in the aspheric surfaces analysis as well as to make the applications that the commercial instruments cannot provide with its own code implemented inside. The algorithm considered two important factors in the instrument-calibration and the aspheric analysis: pickup configuration (pivoted arm) and the stylus radius. It also compensates for the sample tilt and axis offset due to the setup error in the analysis of aspheric surface. The algorithm has been coded by means of C++ and MATLAB. The algorithm was also applied to the real measurement, and compared with the instrument-produced results. Our algorithm found calibration constants better fitting the calibration ball in the instrument-calibration without noticeable cost of the speed. In conclusion, the developed algorithm can cover, and further, shows better performance over the commercial one in both of the instrument-calibration and analysis of aspheric surfaces.