Objective To investigate and evaluate the malnutrition risk and nutritional status of children with cancer from diagnosis to treatment for 6 months To compare the nutritional status of children with lymphoma and solid tumor. Method The nutritional status of 76 children with primary malignant tumors treated in the Department of oncology of Beijing Children's Hospital from July 2019 to November 2021 was analyzed retrospectively. Weight height and upper arm circumference MUAC before initial treatment 1 month 3 months and 6 months after chemotherapy were measured. Nutritional risk screening and nutritional status assessment were conducted at these four time points. The 24-hour dietary intake and blood examination were investigated at the four time points. The complications one month after chemotherapy and nutritional support during 6 months of treatment were collected through medical records. The nutritional status of children with lymphoma and solid tumor were compared. Result The incidence of malnutrition in 76 children before chemotherapy was 15. 8% 12 / 76 32. 9% 25 / 76 at 1 month 25. 0% 19 / 76 at 3 months and 26. 3% 20 / 76 at 6 months after chemotherapy. There were significant differences among the four time points P < 0. 001 . The overweight / obesity rate was 13. 2% 10 / 76 before chemotherapy 7. 9% 6 / 76 at 1 month 5. 3% 4 / 76 at 3 months and 6. 6% 5 / 76 at 6 months after chemotherapy. The difference between the four time points was statistically significant P < 0. 001 There were significant differences in malnutrition score BMI upper arm circumference scan score and total energy intake among the four time points P < 0. 001 . After 3 months of chemotherapy the nutritional status was the worst in 1 month. Comparison between the two groups Six months after chemotherapy dystrophy score 0±0. 9 vs -0. 5±0. 9 BMI 15. 9±2. 1 kg / m 2 vs 14. 8±2. 2 kg / m 2 upper arm circumference 17. 4±2. 0 cm vs 16. 2±2. 9 cm SCAN score 1 1 9 vs 2 1 9 hemoglobin 103. 0±15. 0 g / L vs 94. 2±13. 5 g / L number of malnutrition cases 7 16. 3% vs 13 39. 4% lymphoma group was superior to solid tumor group the difference was statistically significant P< 0. 05 . Conclusion In view of the poor nutritional status of children receiving highintensity chemotherapy nutritional screening and evaluation should be strengthened to find children with nutritional risks as early as possible and actively intervene to improve their tolerance to chemotherapy and quality of life.