In this study, we use the technology of ultrafiltrati on to separate the natural active peptides from milk, and optimize the conditions of ultrafiltrati on. The density of the natural bioactive peptides could be assayed through Biuret method. The results showed that the optimized separation conditions of ultrafiltration are as follows: the temperature 25˚C, pressure 0.25MPa, time 30 min and pH 7, and the membrane flux can reach 14.24 L/m 2 ·h. The concentration of active peptide is 3.78 mg/g by gel filtration chromatography. The method of separating and purifying the natural active peptide from bovine milk has been preliminarily established, which provides a useful exploration for developing functional food and nutritional factors with medicinal value.