Abstract: In the detection process of industrial CT,there exist many factors which can cause incomplete projection data.In such cases,using traditional reconstruction methods(like FBP or EM) directly will not lead to satisfying results.Tangential-CT geometry is one kind of typical situation of incomplete projection data.In this issue,we use iterative method to improve the quality of reconstruction image.We estimate the missing projection data through acquired projection data and make the estimation more and more correct through iteration.Finally we can get an improved reconstruction image.