The invention discloses a preparation method of a 
pepsin-soluble high-purity superhelical-structured type-I collagen, i.e. a low-
antigenicity high-purity superhelical-structured type-I collagen. The preparation method is characterized by comprising the following steps: carrying out alkali treatment on scales which mainly contain the type-I collagen and serves as a 
raw material to remove 
hybrid proteins and fats, then carrying out 
acid treatment to remove 
calcium salts of the scales, adding a weak acid solution as an extraction agent, simultaneously adding 
pepsin, carrying out low-temperature stirring and leaching, and after the leaching is completed, carrying out refrigerated 
centrifugation so as to obtain crude leach liquor of the 
pepsin-soluble type-I collagen; purifying the crude leach liquor of the pepsin-soluble type-I collagen by using a membrane 
separation technology, and freeze-
drying, so that the pepsin-soluble type-I collagen with a purity of not less than 90% and kept at a 
triple helix structure is obtained. A 
collagen product prepared by using the method disclosed by the invention is low in 
antigenicity, clear in configuration, and integral in 
triple helix structure; HPLC detection shows that the product is a type-I collagen with a purity of greater than or equal to 90%, and MALDI-TOF-MS detection shows that a 
mass spectrogram of the product has no impure peak, and the molecular weight is 288 kDa.