Guided by equal strength design ideas, the objective was to improve the fatigue life and prolong the use efficiency of the combine harvester cleaning device by using rigid-flexible coupling dynamics analysis, fatigue life analysis and assembly dimensional tolerance analysis. Through the establishment of the clearing sieve dynamics model, the key factors affecting the fatigue life of the main components of the cleaning device were obtained. The systematic improvement was carried out to improve the fatigue life of the combine harvester cleaning system. A fatigue life analysis method and optimization design method for the cleaning system were proposed. The accuracy of the analysis method was verified by experiments.