Abstract: Whey protein,soy protein isolate and yeast protein concentrate are three kinds of proteins from animal source,plant source and microbial source,respectively. Investigation of the amino acid composition,in vitro digestion and absorption of the three kinds of proteins will be helpful to further understand the nutritional characteristics of proteins from different sources. Amino acid composition analysis and comparison,the digestibility and absorption rates of these three proteins were analyzed and compared by amino acid analyzer and simulator of the human intestinal microbial ecosystem (SHIME). All the three proteins contained 8 necessary amino acids for human,and the composition ratio was close to the FAO/WHO recommended model. The results of the simulated digestion in vitro showed that the gastric digestibility of yeast protein concentrate,whey protein and soy protein isolate was 12.1%±3.8%,33.9%±1.7%,and 23.1%±5.1%,and the digestibility at the end of the small intestine was 92.5% ±2.5%,95.9% ±2.5%,93.5% ±0.3%,respectively. The percentages of proteins absorbed by dialysis in the three groups were 57.3%±2.2%,59.0%±1.8%,58.9%±0.4%,respectively. The digestibility of yeast protein concentrate in the stomach was significantly lower than the others(P< 0.05),and the final digestibility of whey protein was the highest (P< 0.05). There was no significant difference in digestibility between soybean protein and yeast protein(P> 0.05),and there was no significant difference in the absorption of the three proteins(P> 0.05).