A high-precision optical angular measurement method is proposed to measure the torsion angle based on the Moiré fringe produced by double diffraction grating interference.In order to validate the validity of measurement equipment by Moiré fringe,the schematic design and experimental analysis are carried out.The torsional flexibility of a three-dimensional object is simulated by collimator simulation equipment adjusted by a fine-tuning mechanical structure.The measurement experiments are carried out on the independent foundation platform.By comparing different design proposals with experiments,a scheme of CCD target surface installed in the image surface of parallel light is selected to use in this measurement.In this scheme,the image processing technology of filtering thinning is used to obtain the stripe width by treating the collected Moiré fringe,and the torsional flexibility value is calculated by the mathematical model and the changes of stripes width.The experimental results show that the clearer Moiré fringe image can be gotten in the scheme when the collimator is circumgyrated by fine-tuning institution in the field of view of ±7′.And the measuring accuracy of torsion angle is 4.3″(3σ) by the algorithms process when the Moiré fringe width is 1 615~1 712 μm.This method meets the measurement requirements of high-accuracy of torsion angle between equipments,and it lays the foundation to enhance the photoelectric precision of measurement equipment.