The invention discloses a simulation method of concrete crack expansion, belonging to the technical field of computer simulation. The simulation method of concrete crack expansion comprises a process of judging possibly cracking integral points according to the stress state of various integral points and releasing stress and correcting rigidity to the possibly cracking integral points. The process comprises the following steps of: firstly, judging possibly cracking integral points according to the stress states of various integral points; then, selecting the most possibly cracking integral point from the possibly cracking integral points according to the concerned points of a client; carrying out stress releasing and rigidity correcting on the most possibly cracking integral point while keeping the states of other integral points unchanged; redistributing displacement and stress and judging the most possibly cracking point again until no new cracking point occurs. The invention can accurately reflect the overall process of concrete crack from occurrence to expansion and the accurate range of the concrete crack occurrence, keeps the advantages of grid redivision avoidance and simplicity and convenience for calculation of a diffusion crack model, and overcomes the defect that the diffusion crack model is inconsistent with a cracking condition.