An improved Canny algorithm is proposed to remove ring artifacts in Computerized Tomography (CT) images and to improve their qualitative analysis ability and quantitative measurement precision. S-L filter is adopted to filter original projection data and enhance artifact information before using Gaussian filter. Then, the angle thresholds are set to limit gradient direction, and to exclude diagonal direction edge detection and implement vertical direction edge detection. Furthermore, a gradient threshold and an angle threshold are set to detect and connect the marginal point of artifacts. Finally, the piecewise B-spline fitting method is used to correct the projection data and eliminate multiple continuous ring artifacts. Correction experiments are carried out for the actual CT images including ring artifacts. The results demonstrate that the proposed approach can remove all of the ring artifacts of reconstructed images, keep the standard deviation in detail areas basically unchanged, reduce the standard deviation in uniform areas and increase the Signal to Noise Ratio(SNR) by 2.182 dB. The proposed method is effective in correcting not only the multiple continuous ring artifacts but also the single dispersed ring artifacts, at the same time the CT image details and resolution are reserved.