Abstract: In order to understand the relationship between the inner structure and the mechanical properties and the effects of bleaching and dyeing on the mechanical properties of the composite fiber of soybean protein/polyvinyl alcohol,its tensile and relaxation properties were tested.And through analysis,four models——Vangheluwe,modified Vangheluwe,Zurek and modified Zurek were selected,and they were applied to the fitting of the tensile property curves of the composite fiber of soybean protein/polyvinyl alcohol bleached and dyed under different conditions.Through comparison the optimal model suitable for individual case was determined.