Abstract: To better meet the demands of clinical diagnosis and treatment,this paper proposes a CT and MRI image fusion method based on lifting wavelet transform,with different fusion rules employed in low and high frequency sub-bands separately.A fusion rule based on region energy is adopted in low frequency sub-band.Adaptive PCNN fusion rule is adopted in high frequency sub-band,through the application of a simplified PCNN model.The adaptive PCNN uses gradient energy of each pixel as the linking strength of PCNN,so that the linking strength of each pixel can be chosen adaptively according to the change of pixel gradient energy,The high frequency sub-band coefficients are determined by times of firing.The experimental results show that the proposed approach of image fusion achieve better fusion quality with rich information and abundant edge details.