Abstract: In order to model the estimation for the over-sample and sub-pixel imaging considering the detector's filling rate,the detector pixel spread function is derived adversely by the sub-pixel arithmetic.Compared to the over-sample imaging under the 1/m micro-scanning,not only is the sample distance reduced but also the rectangle size of cell detector is compressed to 1/m of the original after the process of sub-pixel arithmetic.Based on the definition of MTF and first-zero frequency,image improvement using sub-pixel arithmetic is larger than the over-sample transform under the same filling rate,and this predominance is boosted up when the filling rate increases.This conclusion in comparison gives evidences in theory for the prospective and advantage of sub-pixel arithmetic imaging.