Incremental photoelectric encoder usually adopts zero position graring providing absolute zero position in order to prevent from data fault during power failure suddenly. Based on theory of generating index pulse, a mathematical model is established. Combining with some objective requirements in the practical applications, the optimal zero-position reticle series is obtained and its luminous flux ratio curve is simulated by using VB language to program with threshold method, which offers a principle and a new realizing approach to design zero-position grating, especially more lines. At the same time, we provide the inversion program in order to give the luminous flux curve of measuring zero-position grating or when it is intercepted or changed, which brings the advantage in measuring zero-position grating. In order to check the feasibility of the method, some examples are given, which prove the zero position reticle serics which fulfills the demands of incremental photoelectric encoder for zero position grating having many advantages such as the maximum residual voltage being lower, peak value voltage being higher. This explains that the method of generating or measuring zero-position grating has many advantages such as reducing operation quantity, lessening degree of programming complexity comparing with enumerating method, and the method also ensures that the zero-position grating has the properties of large luminous flux and high contrast.