Abstract: Radon transform(line integral) is done on lines along known and unknown digital images, with the same line arrangement each line's integral step is constant. Thus easy to acquire integral approximate value("observed value") of each line on digital image; easy to set up a digital image of unknown linear algebraic equations. Use "Algebraic Reconstruction Technique" addition modified iteration to compile Matlab program, with this program to handle the "measurement vector" data and reconstruct unknown digital image. The relative error between calculated results and known digital image is within 2%. This article is basic research of addition modified iteration ART and provides practical application reference for those who interest in "Algebraic Reconstruction Technique".