Abstract: Isoplanatic angle is an important parameter in atmospheric optics field, and it is important for astronomical site optics selection, and evaluation of adaptive compensation for effects of atmospheric turbulence. Past measurement techniques of isoplanatic angle in the world is analyzed, and fundamental measurement principle of isoplanatic angle is introduced. A three annuli mirror was designed and its usability and precision has been verified. Primary specifications was put forward and a prototype has been developed for high precision measurement of isoplanatic angles. The results show that the prototype an measure isoplanatic angle day and night.