This article carries on the optical design and the structural design on one kind entire day aircraft-borne star tracker′s optical lens.It uses Cassagrain refraction and reflecting system,and the angular resolution is 2 angular seconds,optical system's energy concentration degree achieves above 90% in a CCD pixel size,the distortion is smaller than 3‰,the biggest spot′s diameter is 7.6 μm,the others aberration also obtain very good adjustment.To enhance the limiting magnitude which the star tracker surveys,designing a light filter control element.This design satisfies the user to the high accuracy stellar guidance system's demand.