The inflict casualties of UV-irradiation to the isolated protoplasts from thalli ofPorphyra yezoensis were very serious, and UV-irradiation brought some variations in themorphogenitic pattens, developments and color of protoplast-progenies. The material treatedwith low doses, the development and growth of their progenies were promoted, but the higherdoses, the results were opposite. If the protoplasts were treated by colchicine and UV-irradiationtogether, the growth rates of their progenies increased significantly. The higher frequence of purered variants and the abnormal buds in the progenies were obtained. The UV-irradiation resistancewere obvious in the protoplastes and progenies which was treated by colchicine, and the higherconcentrition of colchicine is, the resistance higher is