In this study, four concentrations(1.0, 2.0, 4.0, 8.0 mg/L) of GA3 solution were used to treat the seeds of the semi-dwarf mutant E483, respectively, and the seedlings of E483 were sprayed with 2.0, 4.0, 6.0, 8.0, 10.0, 12.0 mg/L GA3 solution, respectively, and wild-type 6421(CK1) and 0.0 mg/L GA3-treated E483(CK2) was taken as the control. The seed germination and plant phenotype of E483 were investigated under GA3 solution treatment, and the soluble sugar, soluble protein and MDA contents, as well as the activities of SOD, CAT, POD and GR were determined in the leaves of the seedlings. The results showed that the germination potential of E483 seeds was significantly lower than that of 6421 seeds, and the germination potential of E483 seeds treated with 2.0、4.0、8.0 mg/L GA3 solution could be restored to that of 6421 seeds. The height and leaf area of E483 plants were smaller than those of 6421, and the GA3 solution treatment could induce the elongation of the internodes of the stalks, stem thickening, and the increase of the leaf area of E483 but GA3 solution treatment could not change the number of nodes of E483. The plant height of E483 treated with 8.0 mg/L GA3 solution showed no significant difference from that of the 6421. The stem diameter of E483 treated with 2.0 mg/L GA3 solution also showed no significant difference from that of the 6421. Additionally, the leaf width and leaf area of E483 treated with 6.0 mg/L GA3 solution did not significantly differ from 6421. The contents of GA1, GA3, GA20, GA29 and GA34 in E483 seedlings were significantly lower than those in 6421, suggesting that the mutant was a GA synthesis defective mutant. The contents of soluble sugar and soluble protein, as well as the activities of SOD, CAT, POD and GR in E483 leaves, were significantly higher than those of 6421, while the MDA content was significantly lower than that of 6421. The soluble sugar, soluble protein contents and SOD, CAT, and POD activities in E483 leaves treated with 10.0 mg/L GA3 were all the highest.