Abstract: Based on observing the edge of the bright part of the apparent moon by electronic theodolite, a fitting algorithm of the apparent moon center was put forward in this paper, and formulae were deduced in detail. Experiment based on real observation testified the stability of the algorithm, which demonstrated the position of the moon center was solved precisely. Then, a novel method of fast orientation by surveying the moon was explored, with which orientation was realized successfully and both inner and outer precision of orientation could be superior to ±2.0″. The moon-observing method can overcome the shortage that classical astro-geodetic orientation can only be realized by star-observing method at night, and extend the application field of astro-geodetic surveying effectively. Since the apparent sun is a circular plane, the moon-observing method will be suitable for observing the sun. Definitely, fast orientation by observing the moon or the sun has a bright future in application.