Objective To explore the application value of mid-upper arm circumference MUAC and triceps skinfold thickness TSFT in nutritional evaluation of children with tumor. Method From January 2020 to December 2021 162 children with tumor in Department of Pediatrics Union East West Lake Hospital and The Second Department of Pediatrics Huangpi District People's Hospital were selected as the research objects. According to the dual-energy X-ray absorption method the nutritional status of children was evaluated and they were divided into malnutrition group and normal group according to their nutritional status. The levels of MUAC TSFT body mass index albumin and prealbumin in all children were measured. Spearman correlation coefficient was used to analyze the correlation between MUAC and TSFT levels and body mass index albumin level and prealbumin level. The value of MUAC and TSFT levels in diagnosis of malnutrition in children with tumor alone and jointly was analyzed and compared and the diagnostic value was expressed by Kappa value. Result The levels of MUAC TSFT BMI albumin and prealbumin in children with tumor were lower than the reference values. Spearman analysis showed that MUAC and TSFT had correlation with body mass index albumin and prealbumin P< 0. 05 . moreover MUAC had a stronger correlation with albumin in the normal group and the malnutrition group. TSFT had a stronger correlation with albumin in the malnutrition group and with prealbumin in the normal group. Kappa values of MUAC and TSFT were 0. 886 and 0. 897 respectively which were higher than 0. 860 of BMI and 0. 885 of albumin combined with prealbumin but lower than 0. 949 of MUAC combined with TSFT P < 0. 05 . Conclusion Both MUAC and TSFT can be used in the diagnosis of malnutrition in children with clinical tumors but their combined diagnosis has higher clinical value.