Abstract: Effects of cultural conditions on fatty acid composition and content in Spirulina platensis (SP)NS-90020 were studied.With increasing temperature, the relative contents of polyunsaturated fatty acid and GLAin (Sp)NS-90020 decreased,but the content of total fatty acid increased,the absolute contents of total fatty acid and GLAreached the highest level at 40"C,and they were 73.4 mg/g DW, 11.9 mg/g DW, respectively.When NaCIconcentration was higher than 0.0017 mol/Lin the medium, the relative content of GLAdecreased,but lower than 0.0017 mol/Lhad no effect on the fatty acid composition.The absolute contents of total fatty acid and GLAincreased in the presence of amonia,and their highest contents were obtained when amonia was added at the level of 50 mg N(NH,.H,O),they were 67.96 mg/g DW, 13.63 mg/g DW,respectively.The absolute contents 6f total fatty acid and GLAincreased under 92 hours dark treatment during the exponential phase.The absolute contents of total fatty acid and GLAreduced when Fe²⁺, Mg²⁺ or Mo²⁺ was deficient in the medium,but PO₄^3- defienciency elevated the absolute contents of total fatty acid and GLA.