The invention discloses a three-dimensional reconstruction method for a concrete CT (computed tomography) image, comprising the following steps of: firstly, performing tomography on a concrete test sample by a CT machine; secondly, performing three-dimensional reconstruction on the concrete CT image by using a ray-casting algorithm, so as to obtain real images of aggregates, mortar and holes; and finally, performing three-dimensional stereo reconstruction on the concrete CT image by using a visualization tool VTK (visualization tool kit). The three-dimensional reconstruction method for the concrete CT (computed tomography) image, disclosed by the invention, has the advantages of being strong in real-time performance, high in operation efficiency, and capable of clearly and reliably distinguishing the aggregates, the mortar and the holes. A real meso-structure model of concrete can be obtained through a three-dimensional reconstruction result, the three-dimensional reconstruction result can be subjected to a test comparison with a concrete mesoscopic numerical simulation result, and a numerical analysis model is corrected.