Spirulina platensis was mutated by He-Ne Laser (wave length 632 nm,power 10 mW),irradiated for some time,some strains which grow faster than others were chosen to measure the content of β-carotene,protein and polysaccharide,then the strains with high production,high content of β-carotene and protein ext were selected.The result shows that,spirulina platensis sp MS-1,MS-2 and MS-3 which were irradiated by He-Ne laser for 15 min and 25 min,compared with original strain IS,its morphologh parameter changed,morphologh parameter shorted,helix tighted and grow speed was increased obviously.The content of β-carotene of MS-1 was increased by 18.1%,the content of protein and polysaccharide of MS-3 were also increased.In addition,the peak value of original strain was changed compared with the mutant strains by the ultraviolet spectrum of chlorophyll and carotenoid.It showed the mutagenesis domino effect of spirulina platensis by He-Ne Laser.