Objective To understand the incidence of malnutrition and the application of nutritional support in children hospitalized during the perioperative period for digestive system diseases.Methods Children who underwent surgery at Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine related to digestive system diseases with preoperative risk of malnutrition from April 2018 to December 2020 were selected as the studied population. Children were divided into well-nourished, moderately, and severely malnourished groups according to the results of the subjective holistic child nutrition assessment tool (SGNA), and the perioperative nutritional support of children with different nutritional status was compared. Results Three-hundred and ten (310) children were included, 191 males and 119 females, with a median age of 20.7 (6.1-80.6) months. Of the 310 children 124 (40.0%), were malnourished, 99 were moderately malnourished, and 25 were severely malnourished. The difference in age and disease distribution between the well-nourished and malnourished groups was statistically significant (P<0.05), with a higher proportion of the malnourished group correcting for 1 month to 3 years of age and a higher proportion of short bowel syndrome and esophageal hiatal hernia. Among 124 malnourished children, 95 (76.6%) received nutritional support. In the moderately malnourished group, 73 cases received nutritional support; in the severely malnourished group, 22 cases received nutritional support, and the difference in the distribution of nutritional support modalities between the two groups was statistically significant (P<0.05). Compared with children in the well-nourished group, children in the preoperative malnutrition group had longer hospital days and increased total hospital costs (P<0.05). Conclusion The detection rate of malnutrition in children with perioperative digestive system diseases is high, especially in children <3 years old. The rate of nutritional support was higher in children with malnutrition, but there were still cases of non-support.