Objective To assess the effect of early nutritional intervention on the patients with respiratory diseases at nutritional risk. Methods A total of 130 patients with respiratory disease who were hospitalized in Shanghai Fifth People’s Hospital, Fudan University between May 2023 and December 2024 and had a nutritional risk screening 2002 score ≥3 points. Based on the initiation time of nutritional intervention, patients were divided into an early group (≤5 days, n＝65) and a late group (＞5 days, n＝65). Results In the early group, prealbumin (P-ALB) and retinol-binding protein (RBP) levels were significantly higher (P＜0.01), C-reactive protein (CRP), procalcitonin (PCT) levels were significantly lower after intervention (P＜0.05). Compared with the late group, the hospital costs were lower and hospital stays were shorter in the early group (P＜0.001). Spearman analysis showed ALB, P-ALB, and total protein (TP) were negatively correlated with hospital costs (r＝－0.37, －0.20, and－0.22, P＜0.05). RBP, ALB, P-ALB, and lymphocyte count (LYM) were negatively correlated with CRP (r＝－0.30, －0.26, －0.37, －0.18, P＜0.01), RBP, ALB, P-ALB, hemoglobin (HB), and TP were negatively correlated with PCT (r＝－0.23,－0.36, －0.40, －0.30, －0.19, P＜0.05). Conclusions For patients with respiratory diseases, early nutritional assessment should be underwent, and for patients with nutritional risk screening 2002 score ≥3 points, early nutritional intervention could improve the nutritional status and alleviate inflammatory response, promote recovery, shorten the hospital stays.