Abstract: In this paper, the maximal-tree method of the fuzzy graph theory is applied to the numerical classfication research of vegetational regionalism of Shanxi Province,which is divided into 2 vegetational zones, 6 vegetational regions, 17 vegetational plots. Compared with fuzzy clustering analysis and other methods which are used in plant synecology, the maximal-tree method of the fuzzy graph theory produces tree graph from similar coefficient matrices directly so that it avoids the comples compound calculation of similar coefficient matrices. However, the result is not only more audio-visual, but also more satisfactory, Thus we deem it suitable to apply the fuzzy graph theory to vetetational regionalism.