Fill factor is an important parameter for the design of detector arrays, and it′s necessary to research fill factor influence on image quality of micro-scanning system. One model of micro-scanning (2×2) as an example, on the basis of the detailed analysis of micro-scanning can reduce aliasing which is created by detector due to under sampling, output images were simulated with the case of different fill factors. Quantitative analysis on the simulation images from the perspective of image quality assessment was based on structure similarity. The simulation results show that the increase of fill factor can reduce aliasing effect and improve the quality of imaging. Pointed out that fill factor of detector can improve the quality of the image, but the influence on image quality is limited and degree on the improvement of the image was not large, which provide the theoretical and applied research for the design of micro-scanning imaging system.