Abstract: In order to study the feasibility ofisoelectric precipitation method for the purification of collagen from Pacific cod skin,the isoelectric point of the collagen from cod skin was determined by the solubility and the Zeta potential methods. The pH of the crude collagen solution was adjusted to its isoelectric point,and then the collagen was centrifuged,redissolved,dialysed and lyophilized. The SDS-PAGE method was used to determine the purity of the product. The structure properties of collagen were detected by Fourier transform infrared spectroscopy,X-ray diffraction and ultraviolet absorption spectrum. In the end,the process of isoelectric precipitation was optimized by single-factor test.It was found that the isoelectric point of Pacific cod skin collagen was 6.83 and the product was of high purity. The results of spectroscopic properties showed that the triple helix structure of collagen remained intact. The recovery rate was 85% and the purity was over 90% under the optimized condition of pH6.8,6 h and 6 mg/mL collagen concentration. Based on these results,the isoelectric precipitation method is an effective method for purifying collagen.