Abstract: OBJECTIVE To study the gamma-rays mutagenic effects on seeds of Leonurus japonicas Houtt., provide the basis for traditional Chinese medical herb breeding by using gamma-rays radiation. METHODS Physiological and mutagenic effects of gamma-rays on L. japonicas Houtt. dry seeds were studied. The germination percentage, seeding survival, seedling height, root length of M₁ plants and the frequency of leaf color mutation in M₂ generation were selected as criteria. RESULTS The gamma-rays showed obvious inhibitory action to the seedling growth and the ability to induce leaf color mutation. CONCLUSION The gamma-rays is one kind of L. japonicas Houtt. effective mutagens. The appropriate dose is 400-500 Gy for the dry seeds of L. japonicas Houtt.