Abstract: This study selected Spirulina platensis as original strain,and two strains sina032 and sina029 with high yeild and quality were obtained by using the method of capillary suction micro separation to separate per algal filament and combining with UV- Vis spectral scan. Compared with the original strain,biomass of the two strains increased by 44.8% and 39.4% respectively.Content of their bioactivators( chlorophyll,phycocyanin,carotenoids,cis-β- carotene and protein) were oughly the same as that of the original strain.They had better filament form( longer filament,about 20 spiral,bigger pitch) and higher flotation activity.These results showed that the method of separation of per algal filament can be used to screen Spirulina strains with high biomass and high content of bioactivators,which had important and practical significance in the industrial production of S.platensis.