Abstract: The principle of Nonsubsampled Contourlet Transform（NSCT） is studied.A novel fusion algorithm is proposed based on NSCT.Firstly，the CT and MRI images are decomposed at different scales and directions，the low frequency subband coefficients and the the bandpass subband coefficients are obtained.Secondly，different fusion rules are applied in different subband coefficients.The regional energy fusion rule is applied in low frequency subband coefficients and the maximum module rule is applied in the bandpass subband coefficients.Finally，the fused image is reconstructed by the inverse NSCT.The experimental results show that the qualitative of the novel algorithm is better than other fusion algorithms.