Star sensor is a kind of space attitude measurement device whose accuracy reaches arc-second degree, and its imaging module consists of optical lens and image sensor which mainly refers to CMOS APS. The assembly of APS of star sensor is focused, and the influence of spatial position and attitude parameters of APS on the calculation of observation vector is derived theoretically. Thus, a method to control and calibrate these parameters during the process of assembly is proposed, and a corresponding physical system is developed. Test data shows that using this system, the calibration repeatability errors of two components of tilt are ±1.05″ and ±1.09″, respectively, the calibration repeatability error of roll is ±9.4″, and the calibration repeatability errors of two components of eccentricity are ±0.53 μm and ±0.55 μm, respectively.