Abstract: Objective To explore the effects of branched-chain amino acids (BCAA) on the nutritional metabolism, immune function, and inflammatory response in patients with severe burns, and to analyze the differences in their effects among patients with varying degrees of burns.Methods A total of 45 severe burn patients, who were admitted into our hospital from January 2024 to March 2025 were enrolled. The patients were randomly divided into two groups (n=20): an observation group and a control group. Both groups were subjected to standard treatment and routine nutritional support, while the observation group additionally received parenteral nutrition containing BCAA. Nutritional indicators, immune indicators, and inflammatory factors were compared between the two groups after 21 days of treatment.Results During the treatment, the observation group showed significant improvements in nutritional indicators including hemoglobin (Hb), albumin (ALB), prealbumin (PA), transferrin (TRF), and globulin (GLB), as well as a reduction in blood urea nitrogen (BUN) levels (P<0.05), compared with the control group. For immune function, the observation group showed significantly higher proportions of CD3+, CD4+ cells, and CD4+/CD8+ ratio, and a significantly lower proportion of CD8+ cells than the control group (P<0.05). In terms of inflammatory factors, the levels of high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) in the observation group were significantly lower than those in the control group (P<0.05). These effects were observed in both severe and very severe burn patients, but with different manifestations: severe burn patients exhibited early advantages in synthetic metabolism and rapid relief of inflammation, while very severe burn patients showed immune reconstruction and delayed improvement in inflammation under continuous intervention.Conclusions BCAA supplementation can improve the nutritional status, enhance immune function, and reduce inflammatory response in patients with severe burns. It is safe for use and provides evidence for precision nutrition support with stratified interventions.