The invention relates to a compound 
protein fiber and a preparation method thereof. The compound 
protein fiber comprises the following components in percentage by 
mass: 10 to 45 percent of collagen, 10 to 45 percent of 
soybean protein and 10 to 80 percent of 
polyvinyl alcohol. The preparation method of the compound 
protein fiber comprises the following steps of: dissolving the collagen and the 
soybean protein in water, adding the 
polyvinyl alcohol, dissolving, and performing copolymerization modification to obtain 
spinning solution; and performing processes such as wet 
spinning, solidification molding, acetalation treatment and the like to obtain the compound 
protein fiber. The invention has the characteristics that: the compound 
protein fiber which has a high 
mechanical property, a high 
moisture absorption property, high air permeability, a high 
dyeing property, smooth handfeel, soft luster, 
skin intimate performance and health-care performance and is comfortably worn is manufactured by performing blending and copolymerization modification on the 
polyvinyl alcohol by using the collagen and the 
soybean protein; and the collagen and the soybean protein have wide 
raw material resources and low prices, a manufacturing process is relatively simple, and production cost is reduced.