Objective To investigate the perioperative nutritional status of children undergoing operation for malignant solid tumors and its risk factors. Method A total of 60 children who underwent operation for malignant solid tumors at Hainan Women and Children's Medical Center from March 2020 to March 2023 were enrolled. They were divided into malnutrition group and non-malnutrition group according to the nutritional status in 3 months after operation. The perioperative nutritional status of children undergoing operation for malignant solid tumors and the risk factors for malnutrition were analyzed. into malnutrition group and no malnutrition group. The perioperative nutritional status and risk factors of malnutrition in children undergoing surgery for malignant solid tumors were analyzed. Result In 3 months after operation there were 32 53. 33% children without malnutrition and 28 46. 67% children with malnutrition. BMI FFMI and BCMI in the malnutrition group were lower and FMI was significantly higher as compared with the non-malnutrition group P= 0. 005 P = 0. 004 P<0. 001 P = 0. 007 . Compared with the non-malnutrition group the proportions of children undergoing radiotherapy and chemotherapy after operation and children with medium-risk and high-risk nutritional status at admission were significantly higher. During hospitalization the dietary intake meets the standards and the proportion of special nutritional support is significantly lower in the malnutrition group P < 0. 001 P = 0. 001 P < 0. 001 P = 0. 006 . Postoperative radiotherapy and chemotherapy and nutritional status at admission were risk factors for malnutrition in children undergoing operation for malignant solid tumors P = 0. 017 P = 0. 029 . Conclusion The perioperative nutritional status of children undergoing operation for malignant solid tumors is not good and the risk of postoperative malnutrition is high. It is necessary to strengthen nutritional support for children with poor nutritional status at admission and those undergoing radiotherapy and chemotherapy after operation.