With the changes from optical imaging to digital imaging, how to improve the geometric resolution of CCD has become a problem urgent to be solved in developing a high-resolution electrical imaging system. A mathematic model for imaging on super-resolution and sub- pixel was built, a method to improve the geometric resolution of CCD based on sub-pixel was presented, in which two linear CCDs staggered by half dimension of the pixel in the line direction are integrated in one component, while the reading out time is reduced to half; At last, the image data is interweaved to synthesize a high resolution image. Two methods, bilinear interpolation and sub-pixel imaging, were simulated with the software MATLAB. The effects of the two methods were analyzed qualitatively and quantitatively. The results show that with sub-pixel imaging method, the resolution of synthesized image is twice as large as that of low-resolution image, and the PSNRs in the two groups of simulating images are enhanced by 1. 486 4 dB and 2. 207 0 dB compared to that in bilinear interpolated image. Sub-pixel imaging method could mitigate greatly the image blur induced by under sampling, and the elapsed time is less than the bilinear interpolation method.