Collagen is one of the predominant proteins in the living body,and the essential protein component in connective tissue.Compared with collagen from land animals(such as pig,cow),aquatic collagen has drawn extensive attention for its excellent physiochemical properties and physiologically active functions.Chinese softshelled turtle(Pelodiscus sinensis)is a rare and precious traditional aquatic animal in China.It has a high medicinal and nutritional value with plenty of calipash collagen.The collagen from calipash of P.sinensis was extracted by pepsin digestion under acid condition.The effects of pepsin addition,substrate concentration and extraction time on yield of collagen were investigated.5 mg/mL pepsin addition,4% substrate concentration and 14 hours extraction time were established as optimal conditions for preparing calipash collagen.The extracted crude collagen was purified by salt precipitation and dialysis,and then its biochemical characterization was determined by the methods of SDS-PAGE,DSC,UV and FT-IR scanning.The result indicated that the extracted calipash collagen was of high purity and belonged to typical collagen Ⅰ with two α and one β chains.It can be assumed that the calipash collagen of P.sinensis might be a useful substitute for porcine and bovine collagens.This study laid a scientific foundation for further exploitation and utilization of the calipash collagen polypeptide of Chinese softshelled turtle.