Abstract: Ultraviolet lunar sensor is an imaging attitude sensor which has the wide FOV.(Aiming) at the attitude determination algorithm,analyzed the validity and limitation of the(conventional) circle algorithm used by MOSAIC Sensor.Pointed out that the geometric center of(lunar) image can't be regard as the nadir point in the low orbit.A new algorithm was developed throw the tailor equation based on the imaging analysis.The new algorithm can supply the high precise attitude data even in the low orbit.The simulation results prove this algorithm is valid.