Large photo-electricity telescope plays a more and more important role in exploring objects in the space and astronomy observation, its detectivity and pointing precision are the main factors that affecting its development. Firstly, detailed analysis on different errors affecting the pointing precision of the telescope was conducted in the paper; then topology of the telescope was constructed and the spatial error pointing model was established based on multi-system theory; finally the relation between three axis differences and angle measurement errors was researched. Compared with traditional spherical function, a comprehensive item of errors were contained in the model which provided reference for error distribution and error correction.