Abstract: Single factor experiments were carried out to investigate the effects of different alkali solution p H, alkali solution time, alkali solution temperature and solid-liquid ratio on the extraction rate of protein from fermented soybean meal. The optimum extraction technology of protein from fermented soybean meal was established by response surface optimization, the main quality index of the extracted protein was measured. The results showed that the effect of different factors on protein extraction rate was in the order of alkali solution time > alkali solution p H > alkali solution temperature > solid liquid ratio.The optimal process was as follows: alkali solution pH9.4, alkali solution time 56 min, alkali solution temperature 41 ℃, solid-liquid ratio 1∶12.Under these conditions, the extraction rate of the modified protein was 60.36%. The results showed that the solubility, in vitro digestibility and acid soluble protein content of soybean protein isolate (SPI) extracted from soybean meal fermented by Lactobacillus plantarum were significantly higher than that of non fermented soybean meal (p < 0.05) . It was economical and easy to use this technology to extract fermented soybean meal protein, and the quality of SPI was good, which could provide reference for the development and utilization of soybean meal protein.