Presented is a method of relative stress spectrum used in predicting the fatigue life of the structure of a construction machinery. The method can be used hi fatigue life prediction of the operating device of the wheel loader under various conditions. 提出了一种用于工程机械结构疲劳寿命预测的相对应力谱方法,并用该方法进行了不同情况下的装载机工作装置疲劳寿命的预测分析。