It was found that the concentration of SCFAs in the colonic cavity of GF mice was decreased, and the expression of Foxp3 and IL-10 was increased after treatment with propionate. When treated with a combination of vancomycin and SCFAs, the reduction of Treg cells was completely restored. By constructing a model of T cell transfer in colitis, it was found that the frequency and number of Foxp3+Treg cells increased in mice receiving the propionic acid and SCFAs mixture. The gene discussed is FOXP3; the disease is colitis.