A new zero optical path difference (OPD) point positioning technique using diode lasers is proposed in this poper. With the linear frequency modeulation property of a diode laser and the technique of dual-wavelength refinemenr, the zero OPD point of a interferometer is dynamically searched with a very high accuracy of 0. 01 micrometer. Compared to that of the traditional white light positioning, the interferometer of diode laser positioning is simplified, and the searching range of the zero OPD point has been increased greatly.