【Objective】 To investigate the correlation of serum 25-hydroxyvitamin D3 [25-(OH)D3], albumin (ALB) and ferritin (SF) with Screening Tool for the Assessment of Malnutrition in Pediatrics (STAMP) score in preschool children with malnutrition, and to analyze the predictive value of these factors on clinical outcomes, so as to provide reference for improving clinical outcomes. 【Methods】 Totally 90 preschoolers with malnutrition in Fuzhou Children′s Hospital from August 2021 to August 2022 were selected as the observation group, and 60 healthy preschool children during the same period were selected as the control group. Nutritional guidance was provided to the preschoolers for a consecutive 3-month period, followed by monitoring and recording the incidence of malnutrition and iron deficiency anemia within 3 months after treatment. 【Results】 The levels of serum 25-(OH)D3, ALB and SF were lower in the observation group compared to the control group, while the STAMP score was higher in the observation group (t=9.700, 6.047, 4.771, 26.976, P<0.05). The levels of serum 25-(OH)D3, ALB and SF in preschool children with malnutrition showed a negative correlation with the STAMP score (r=-0.813, -0.792, -0.829, P < 0.05). After 3 months of treatment, the levels of serum 25-(OH)D3, ALB and SF, as well as the difference between pre- and post-treatment levels, were lower in children with adverse clinical outcomes compared to those with good clinical outcomes (t=3.622, 2.189, 2.163, 8.704, 4.354, 5.296, P< 0.05). When the difference in serum 25-(OH)D3, ALB and SF before and after treatment was small, preschool children with malnutrition had a higher risk of adverse clinical outcomes [25-(OH)D3:OR=7.250, 95%CI: 3.008 - 17.476; ALB: OR=9.167, 95%CI: 2.954 - 28.444; SF: OR=5.730, 95%CI: 2.364 - 13.890]. The combined predictive value of serum 25-(OH)D3, ALB and SF before and after treatment had an AUC value of 0.927, higher than that of any single index. The decision curve analysis (DCA) showed that the combined prediction scheme of these factors had a clinical net benefit in predicting the clinical outcome of preschool children with malnutrition. 【Conclusions】 Low serum levels of 25-(OH)D3, ALB and SF are indicative of a higher risk of adverse clinical outcomes. Utilizing the combined prediction of these factors before and after treatment shows high accuracy in predicting clinical outcomes.