Objective:To study the test condition of using rare earth elements to cultivate Spirulina with high-content DHA.Methods:L₉(3⁴)orthogonal test was used to do the study.Four kinds of rare earth elements,such as lanthanum(La),cerium(Ce),neodymium(Nd)and samarium(Sm)were set as the four factors while each factor set three levels.The content of DHA in Spirulina was detected as index to appraise the effect.Comparison test was done between the new method and the old method.Results:Spirulina had a high content of DHA under the condition of La³⁺10mg/L、Ce³⁺1mg/L、Sm³⁺2mg/L、Nd³⁺10mg/L,which was 58.0% higher than that of cultivating spirulina without rare earth element.Conclusion:An appropriate amount of rare earth element has a promoting effect on increasing the content of DHA in Spirulina.