When the computer tomography (CT) image is reconstructed,the signal-to-noise ratio of the C T image becomes low.This paper presents a low-dose medical CT image denoising a lgorithm based on discrete shear wave (map Markov random field,MAP-MRF).Firstly ,using the advantages of multi-scale and multi direction of discrete shear wav e ,the shear coefficient can be calculated accurately,and the image information can be expressed sparsely.Combining with Markov theory,a denoising algorithm b ased on MAP-MRF is proposed,which makes the blind restoration result achieve a n effective balance in noise elimination and edge preservation,and optimizes the regularization term,so that the algorithm converges quickly.The image noise h as been effectively filtered out,and the image features have been well preserve d.The qualitative and quantitative experiments of Shepp Logan body membrane,cl inical brain CT and clinical low-dose shoulder CT with MAP-MRF algorithm and o th er five comparison algorithms are carried out.The experimental results show tha t this method can obtain good CT reconstruction images and retain clear texture details and structure in the qualitative experiments In the quantitative experim ents of 10mA simulated noise and 20mA clinical low tube current,the PSNR and S SIM indexes are greatly improved,and the root mean square error (RMSE) is lower than the comparison algorithm,which proves the effectiveness of the algorithm.