Objective: To observe the effects of recombinant human growth hormone (rhGH) combined with enteral nutrition support on respiratory mechanics, immune function and weaning success rate in elderly patients with chronic obstructive pulmonary disease (COPD) complicated with pulmonary infection and mechanical ventilation. Methods: A total of 104 elderly patients with COPD complicated with pulmonary infection and mechanical ventilation admitted from June 2022 to June 2025 were selected and divided into two groups at a ratio of 1:1. Both groups received conventional symptomatic treatment. The nutrition group was treated with enteral nutrition support, and the rhGH group was treated with rhGH on the basis of the nutrition group. The respiratory mechanics pressure indicators, immune function indicators, nutritional indicators, inflammatory indicators, mechanical ventilation time and weaning success rate were compared between the two groups. Results: There was no significant difference in respiratory mechanics pressure indicators before treatment between the two groups (P > 0.05). Compared with before treatment in the same group, the airway peak pressure, intrinsic positive end-expiratory pressure and plateau pressure decreased in both groups after treatment, and the respiratory mechanics pressure indicators in the rhGH group were lower than those in the nutrition group (P < 0.05). There was no significant difference in immune function indicators and nutritional indicators before treatment between the two groups (P > 0.05). Compared with before treatment in the same group, CD8+ decreased in both groups after treatment, and the rhGH group was lower than the nutrition group (P < 0.05); CD3+, CD4+, CD4+/CD8+ and albumin (ALB), prealbumin (PA), retinol binding protein (RBP) increased in both groups after treatment, and the rhGH group was higher than the nutrition group (P < 0.05). There was no significant difference in inflammatory indicators before treatment between the two groups (P > 0.05). Compared with before treatment in the same group, macrophage inflammatory protein-1α (MIP-1α), tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), and high mobility group box 1 (HMGB1) decreased in both groups after treatment, and the rhGH group was lower than the nutrition group (P < 0.05). The mechanical ventilation time in the rhGH group was shorter than that in the nutrition group, and the weaning success rate was higher than that in the nutrition group, with significant differences (P < 0.05). Conclusion: rhGH combined with enteral nutrition support in elderly patients with COPD complicated with pulmonary infection and mechanical ventilation can shorten the mechanical ventilation time, improve immune function and respiratory mechanics, reduce inflammatory response, and increase the weaning success rate.