Abstract: Intra-abdominal infections (IAIs) are common in the clinical practice, which include a variety of patholo-gical conditions. Severe IAIs can lead to sepsis, secondary organ dysfunction, and threaten the lives of patients. Patients with IAIs are under a high metabolic reaction, and often have gastrointestinal dysfunction, manifesting as impaired intestinal mucosal barrier function, out of control in intestinal flora regulation, and continuous loss of nutrients. The body is in a malnutrition condition, and body resistance severely declines, which further aggravates disease progression. Intestinal micro-ecology is the largest and most complex ecosystem in the human body. In the case of coexistence of many bacteria, the synergy and antagonism between different strains maintain the balance of digestive tract microecology. Intestinal flora and nutritional status under IAIs have their particularity. Understanding the mechanism of intestinal flora abnormalities under IAIs, reasonable and effective nutritional support treatment and management is essential for improving the prognosis of patients with IAIs.