Abstract: The three-dimensional reconstruction concrete model based on CT slices can provide a better research model for revealing concrete failure mechanism. Having taken CT slices of a concrete section, the reconstruction technology for a three-dimensional (3D) concrete model is mainly studied in the paper by the digital image technology and MATLAB image treatment tool. The pore in the concrete is taken into consideration in the model, the CT slice of the concrete section is composed of three-value pixels by bottom cap treatment, and the 3D structure of concrete specimen is reconstructed, based on the method of volume data. The controlling factors of unit attributes are studied in detail, based on the method of mesh mapping. A more accurate judgment criterion of unit attribute recognition is proposed, and the 3D finite element mesh model with the same aggregate proportion as the specimen in the experiment is established, and the four-point bending-tension fracture process for the reconstructed beam is analyzed by the nonlinear FEM. Numerical results show that the bending curve and failure shape of the reconstructed model are quite identical with the those of the experiment.