In this study, isoelectric point precipitation method and ultra-filtration purification technique was used to purify the collagen type I extracted from bovine tendon by using acetic acid and pepsin with low temperature. Tannic acidprecipitation and SDS-PAGE gel electrophoresis demonstrated that isoelectric precipitation could effectively remove pepsin; The purified collagen type I had a maximum absorption peak at 235 nm in Ultraviolet spectroscopy; SDS-PAGE spectra showed three characteristic bands of collagen type I; The Kjeldahl method also confirmed that the collagen purity was in line with the standard(YY/T 1511-2017); Fourier transform infrared spectroscopy andcircular dichroism confirmed that the triple helix structure of collagen was completely preserved. The data means the high purity of collagen type I and the integrity of the triple helical structure can be insured by the isoelectric precipitation method combined with ultra-filtration purification technique.