In order to improve the working performance of cassava harvester, multi-objective optimization design for the rack of the harvester was conducted. Under the CAD/CAE integrated design platforms, the statics finite element analysis and sensitivity analysis of the original rack were executed. Based on the above analysis, the multi-objective optimization design model for the rack was built, and six groups of non-inferior solution were obtained. From six groups of optimization design schemes and original design scheme, the optimal design scheme was selected by using fuzzy matter-element method and entropy-weight method. Comparative analysis on rack before and after optimization design showed that the rack’s mass reduced 4.29% and the maximum deformation reduced 27.04%, which proved that the proposed structural optimization design method for cassava harvester’s rack based on sensitivity analysis was reasonable and feasible.