A project management method and a system thereof are provided. The method adapted for a project network model with multiple edges includes following steps: obtaining multiple assignment values of each edge, multiple state distributions corresponding to the assignment values, a connecting configuration between the edges, and an assignment upper bound and a demand level of the project network model; enumerating at least one project path composed of the edges; enumerating at least one critical value assignment vector according to the assignment values of each edge and the assignment upper bound; calculating a project reliability for each critical value assignment vector according to the at least one project path; and, selecting a critical value assignment vector with a maximal project reliability of the at least one critical value assignment vector to perform a value assignment for the project network model. |