In order to break through the current limitation of simulation accuracy for the ultrasonic detection of TATB based PBX and to realize the structure-performance relationship based nondestructive ultrasonic testing and characterization， an ultrasonic simulation method based on CT image modeling （MBCT） was proposed. Using the significant difference of gray-level distribution between the particle phase and the binder phase in CT images， the structural morphology and features of the sample were extracted. A two-dimensional geometric structure model containing molding powder particles and boundary morphology was obtained by processing the CT slice image with noise reduction， binarization and boundary optimization. Then， the model was used for finite element simulation of ultrasonic propagation， and the differences between MBCT and conventional Voronoi model were quantitatively compared. Results show that the MBCT can effectively and precisely describe the random complex structure characteristics of TATB particles and boundary morphology， which makes the ultrasonic simulation results have better consistency with the experiment ones. The errors of sound velocity， attenuation， frequency domain amplitude and apparent integrated backscattering （AIB） coefficient were 0.32%， 1.14%， 0.92% and 1.55%， respectively （within 2%）. Compared with Voronoi model（2.77%， 35.93%， 20.70%， 13.68%）， the error is greatly reduced， and the simulation accuracy is significantly improved.