Abstract:The effect of chronic irradiation on soybean seedlings was studied.The results showedthat under 30Gy and 50Gy with the dose rate of 0.0146,0.0051 per min respectively,the chronic irradiation evidently inhibited the growth,development and seed yield of soybean。Some variations which had never been seen appeared,In M1 generatiou one or threeleafletswere observed frequently. In M2 generation,one or three cotyledens and unifoliolateleaf of soybean plants were observed at seedling stage。some seedling were stunted with crin-kled or linkded cotyledens,Tbe results also indicated that the dose rate of 0.0051Gy per min had higher irradiation effect tban the dose rate of 0.0146Gy per min in same dose level。Chronic irradiation at VE-V1(emergence-first node)stage could induce genetic muation onprotein content of soybean seeds.A mutant with 50.02 percent of protein was selected fromprogenies of M5 generation treated with dose of 50Gy。