Abstract: To study the effects of plant hormones on the seed dormancy and germination of Leymus chinensis, three exogenous hormones including Abscisic acid (ABA), Gibberellin 3 (GA₃), Gibberellin 4+7 (GA₄₊₇) and their biosynthetic inhibitors were used to treat seeds. Seed germination was not affected by low exogenous ABA concentrations, but was significantly reduced at the highest concentration. This reduction was reversed by FL application indicating that ABA biosynthesis may play a critical role in maintenance of seed dormancy. The type of gibberellin affected its effect: GA₄₊₇ significantly promoted seed germination, but GA₃ had no effect. Percentage seed germination significantly decreased after immersion in PA which is a biosynthesis inhibitors of GA, but this effect can be reversed by exogenous GA₃. This shows that GA is necessary for non-dormant seed germination. This was further confirmed by a combination of PA plus FL treatments, which inhibited ABA biosynthesis during imbibition, although the percentage seed germination still decreased. In addition, 8 weeks cold stratification in FL can significantly break seed dormancy of L. chinensis, but other media can induce secondary dormancy, a process that may be related to an increase of ABA during imbibition.