Abstract: From the regenerated blades of single somatic cells isolated enzymatically from a blade collected from the cultivation ground of Porphyra haitanensis Chang et Zheng,the fastest growing blade was selected for isolating somatic cells,and was cultured for getting regeneration blades again.From its regenerated blades,the fastest growing blade was isolated.After 3 times of selections continuously in this way,we got an improved strain named XS-1,characterized by faster growing,later maturation and higher contents of phycobiliprotein as compared with the wild type(wt)strain.After 80 days in culture,the mean length of F₁ gametophytic blades of XS-1 grew up to 128.8 cm,which was 10.5 times faster than those of the wt.The maturation peak of F₁ blades of the XS-1 delayed about 20 days later than the wt.In the wavelength of 350-750 nm, in vivo absorption spectra of the F₁ blade of the XS-1 was similar to the wt, showing five absorption peaks but having higher absorption value in every peak than the wt.The contents of phycobiliprotein(PE+PC)and Chl. a in XS-1 were 80.4 mg/g and 8.9 mg/g,increasing by 188.8% and 32.5% compared with the wt, respectively.Mean thickness of the F₁ gametophytic blades of XS-1 was 32.2 μm,decreasing 15% compared with the wt.In short,the XS-1 is a fast growing strain that may offer broad applications for the nori industry.