Abstract: Based on the traditional Shark-Hartmann wave-front measurement, a wave-front measuring method suitable for large scale telescope system was proposed. A set of pentagonal prism beam turning devices were introduced to transfer quasi-reference beam to scan every sub-aperture, and an improved S-H sensor was used to measure the wave-front of every sub-aperture. The wave-front measuring errors, which were induced by the manufacturing and kinetic errors of pentagonal prism, were theoretically analyzed and proved to be correct by a wave-front compensation method. The errors of self-wavefront of large scale telescope was reproduced availably. The method can be applied to measuring the wave-front of large scale telescope.