In order to further highlight the details of medical image fusion and improve the clarity,this paper proposes a medical image fusion algorithm based on UDWT and PCNN in NSST domain.In this alg orithm,the source image is decomposed by NSST to obtain low-frequency and high-frequency subband coeffici ents.In the low frequency fusion rules, the low frequency sub-band is further decomposed into energy sub-band and deta il sub-band by UDWT,and the low frequency energy sub-band corresponding to the two source images is fused by PC NN; the low frequency detail sub-band of the two source images is fused by region energy and the low frequency detail sub -band of the fusion source image,and then the inverse UDWT is applied to fuse the low frequency detail sub-band and energ y quantum band.Secondly,in the rules of high-frequency fusion,the high-frequency sub-band corresponding to A and B s ource images is further decomposed into high-frequency energy sub-band and high-frequency detail sub-band by UDWT,a nd then the fused high-frequency sub-band is obtained according to the combination of Laplace energy and regiona l energy.Finally,the fusion sub-band is obtained by inverse NSST.Experimental results show that the proposed algorithm has greater advantages in visual effect and objective indicators compared with the existing mainstream algorithms.