Abstract: Arthrospira platensis A9 strain in log phase was broken to 2 cells ~4 cells fragments by 40 s pretreatment of ultrasonics, the sample was mutagenized by ultraviolet (UV) and 60Coγray, and then the samples were inoculated into liquid and solid Zarrouk Medium after 3 h pre-incubation. With the dosage of radiation increasing the survival ratio of samples were decreased dramatically and under the condition of UV for 70 s and 60Coγray for 3500 Gy no growth occurred on plates, whereas the growth of the samples with high dosage treatment could somehow resumed in liquid. The samples mutagenized were inoculated to liquid medium with 20 μg·mL-1ρ-fluorophenylalanine (FPA) and 20 μg·mL-1 L-canavanine sulphate (CS) respectively in a light incubator for 3 day ~ 4 day, and then spread on plate with the same concentration of FPA and CS. The resistant mutation rates were calculated after growing for about 30 day.