The strain time history of the strain simulation control point in the lower suspension arm was measured when the car was driven on the intensified road in Hainan automobile proving ground. Then the frequency analysis was done, and the service conditions for quasi-static method were also discussed. Combining finite element static analysis result, the stress time history of the critical location was gained by quasi-static method. Fatigue life of lower suspension arm was evaluated by the nominal stress method. Based on these work, the effect exerted by the choice of the strain simulation control point and the effect of average stress revised arithmetic on the result were investigated. The conclusion is helpful to well choose the strain simulation control point, and has reference value to improve the accuracy of analyzing fatigue life. Although the research in this article is to take the lower suspension arm for an example, the research method and conclusion have also reference value to other parts.