As one of the important components of milk， β-casein has high nutritional value. Due to genetic mutations， beta-casein appears in many variant forms， with the most common genotypes currently being A1 and A2. The A1 and A2 variants affect the structure and digestion of the protein due to differences in the single amino acid 67th. In this study， casein was first extracted from A1 and A2 milk by isoelectric point precipitation， and then β-casein was purified and identified by anion exchange chromatography and polyacrylamide gel electrophoresis. Finally， a digestive system was constructed to analyze the properties of A1 and A2 β-casein digestive products. The results showed that the mass concentration and purity of A1 and A2 β-casein were 0.58 mg/mL and 0.64 mg/mL， respectively， and 92.45% and 94.21%， respectively. After simulated gastrointestinal digestion in vitro， the digestibility of A2 β-casein reached 94% at 4.0 h， while that of A1 β-casein reached 93.47% at 5.0 h. With the increase of gastrointestinal digestion time， the particle size of A2 β-casein gradually decreased and was decomposed into substances less than 100 nm， while the particle size of A1 β-casein was still concentrated in the larger range of 100-500 nm. With the progress of digestion， the content of essential amino acids increased gradually， and the degree of hydrolysis increased rapidly during enteric digestion， and the content of β-fold structure decreased， and the disordered structure increased. These results suggested that A2 β-casein may be more conducive to gastrointestinal digestion than A1 β-casein.