Abstract: This paper reviews two main categories of reconstruction algorithms in parallel CT and fan-beam CT,and introduces the approachs to implement them on PC.In order to speed up CT scan and reconstruction,based on the analysis of the beam geometries relationship between parallel scan and fan-beam scan,the paper introduces a special scan model named short-scan which differ from traditional full-scan,and proposes an approach named parallel re-sorting to reconstructing images from short-scan fan-beam data.And then realizes it.According to experimental results,we find that reconstruction speed is improved remarkably.