Abstract: In order to investigate the mutagenic effect of ⁶⁰Co-γ irradiation on oil flax seed, three ⁶⁰Co-γ doses of 800 Gy, 1000 Gy and 1200 Gy irradiations were treated on seeds of 6 cultivars （lines）, and the effects of irradiation on seed germination, agronomic and quality traits were examined, to determine the optimal irradiation dose of flax. The results showed that using ⁶⁰Co-γ treated oil flax seed, the germination energy, germination rate, plant height, technical length, seeds per boll, 1000-seed weight, the content of oil, linoleic acid, oleic acid and palmitic acid were all lower than those of the control. And the effective tiller, effective branch, bolls per plant, lignan, linolenic acid and stearic acid content were all higher than control. With the increase of irradiation dose, the germination energy, germination rate and lignan content gradually decreased, the root length, seedling height, fresh weight per plant, oleic acid content decreased firstly and then increased, the plant height, technical length, effective branches, bolls per plant, 1000-seed weight, linolenic acid, stearic acid andpalmitic acid content increased firstly and then decreased, effective tiller, bolls per plant, seeds per boll, no seed bolls, oil content and linoleic acid content were increased with the increasing of the dose. The inflection points all appeared in 1000 Gy, and there were obvious differences among varieties. The theoretical optimal irradiation dose of flaxseed was 1029 Gy. Elit materials occured about 10% to 21% when the seeds treated with ⁶⁰Co-γ irradiation. And high lignan content seemed easy to be found, followed by the linolenic acid content, and finally the oil content. High dose （1200 Gy） was beneficial to the variation of oil content and linolenic acid, while low dose （800 Gy） was beneficial to the variation of lignan. These results can provide theoretical basis for eseirradiation breeding and germplasm innovation of flax.

Key words: ⁶⁰Co-γ, irradiation, oil flax, mutagenic effect