Abstract: When the cotton picker is working, the frame vibration will be caused by the load excitation. When the excitation frequency is within the natural frequency range of the frame, the resonance phenomenon will occur, which will affect the cotton picker. In order to improve the working performance of the cotton picker, this paper conducts modal analysis on the frame of the cotton picker and obtains the first six modal parameters of the frame. By analyzing the excitation characteristics of the vibration source, it is found that the first and third modal frequencies of the frame are in the excitation interval of the vibration source, and the frame quality is set as the optimization target, and the dimensions of the frame are set as design variables. The sensitivity analysis of the rack is carried out based on CCD sampling design and Kriging method is used to fit the response surface. Five optimization schemes are obtained by using multi-objective genetic algorithm. Combining entropy weight method and linear weighting method, scheme 1 has the highest comprehensive score and is the best design scheme. After optimization, the first-order mode frequency of the rack is reduced from 97Hz to 91Hz, the fourth-order mode frequency is increased from 225Hz to 230Hz, and the excitation frequency away from the engine is 100Hz and 220Hz. The mass is 688.8kg reduced by 1.5%. It is verified by statics and harmonic response analysis that the optimized frame meets the working requirements.