The present invention relates to the field of medicine, and relates to an application of a PDE9A inhibitor in the preparation of products having an elevated Treg content, drugs for preventing and treating inflammatory bowel disease, and health care products. The PDE9A inhibitor may improve the secretion of mucosal mucus in an intestinal tract suffering from inflammatory bowel disease, reduce the secretion of TNF-α, IL-6, IL-17 and IL-12/IL-23 pro-inflammatory factors, inhibit DC cell differentiation and migration, increase the ratio of Foxp3+Treg cells, and promote the movement of CD4+CD25+Treg cells from the spleen and mesenteric lymph nodes to the colon, thereby inhibiting an intestinal inflammatory response and controlling the occurrence and development of the disease. When the PDE9A inhibitor is applied to a drug for preventing and treating inflammatory bowel disease, inflammatory bowel disease may be effectively prevented, alleviated and treated, while healthcare products containing said inhibitor as an active ingredient may regulate the intestinal tract of patients suffering from inflammatory bowel disease and control the occurrence and development of inflammatory bowel disease.