Aimed at the problem that the research and development of peanut silage coated silage equipment in China is not perfect, and the joint harvest of peanut fruit seedlings can not be achieved, a fixed straw bale film device was developed on the basis of the 4HB-2A peanut combine harvester. A polyethylene stretched film with width of 25cm and thickness of 25μm was taken as object. By analyzing the elongation rate and overlap rate of the envelope, it was determined that the stretch rate and the overlap rate of the stretched film were 50% when the bale was wrapped. The film guide mechanism was designed according to the requirements of the elongation rate of the stretched film. The torsion angle of the torsion spring τ>68° and the film roll angle θ>108° were obtained through the force analysis of the film guide mechanism. Based on the analysis of the bale specifications, the transverse shrinkage of the stretched film, and the overlap of the envelope, it was determined that the rotation speed ratio of the device rotation and the rotation of the bale was 18. Through the transmission cooperation relationship of the coating device and the design of the bearing drum, the rotation speed ratio of the device rotation and the bale rotation reached the expected value. Based on ADAMS, the lift angle of the pneumatic cylinder of envelope device was simulated, and the lift angle of the device was determined to be 66°. The field performance test results showed that the fixed film device had a stretched film elongation rate of 51.4%, and the film efficiency of the twolayer, fourlayer and sixlayer coatings was 10.5s/layer, 8.4s/layer and 7.6s/layer, respectively. The coefficients of variation of uniformity were 12.20%, 7.70% and 4.70%, respectively. All indicators met the qualified standards, and the quality of coating can meet the requirements of peanut seedlings silage.