Abstract: Though CT technique has been developed more than forty years,there are many difficulties in large object CT imaging,high-resolution imaging and how to reduce X-ray dose.In fact,in stead of full images for the whole object,the images of region-of-interest(ROI) are enough in many CT imaging applications,especially in medical clinical imaging according to the lesion organs.This paper focuses on ROI image CT reconstruction algorithms and X-ray field-of-view design.The key problem of ROI reconstruction is how to exactly and stably reconstruct ROI images from the truncated projection data.This paper introduces reconstruction algorithms for three different kinds of truncation cases.Numerical experiments were done to validate the above algorithm.Finally,we discuss the application prospects of the ROI CT imaging technique.