Ultraviolet lunar sensor, a part of CE lunar orbiting satellite, is a wide-field of view optical image sensor that references to the attitude of the moon. In order to ensure high coaxiality and symmetry of both annular and central fields, high coaxiality machining of the flange hole (central hole) for the octahedral pyramid mirror of the Ultraviolet lunar sensor is needed. Furthermore, high coaxiality assembly of the octahedral pyramid mirror and the objective lens are needed. The conventional method achieves the goal by changing washer thickness. It has obvious disadvantages such as alignment iteratively and lower precision. This paper presents a high-precision lens centering method for octahedral pyramid mirror. This method can find mean square neutral surface quickly and accurately, and realize precision machining of the flange hole (central hole). After the lens centering of the objective lens, the high coaxiality assembly of the octahedral pyramid mirror and the objective lens can be achieved. Experimental results demonstrate that the reflection image error of octahedral pyramid is 17.3″, it′s better than expected value 30″, and the coaxiality of flange hole and the end face runout are less than 0.005 mm The symmetry for the field of view of the octahedral pyramid relative to the center field of view of the objective len reaches 0.01 mm. This alignment of sensor has got verified successfully at CE-1 spacecraft′s space mission.