Objective To investigate the effect of pulmonary ultrasound‑guided lung re‑expansion versus conventional lung re‑expansion on postoperative pulmonary complications in elderly patients undergoing laparoscopic gastric cancer surgery. Methods A total of 80 elderly patients, 42 men and 38 women, aged≥65 years, BMI 18−30 kg/m2, ASA classification grade Ⅰ−Ⅲ, who underwent elective laparoscopic gastric cancer surgery from March 2022 to June 2022 were selected. According to the random number table method, they were divided into two groups (n=40): a conventional lung resuscitation group (group R) and a pulmonary ultrasound‑guided lung re‑expansion group (group LUS‑R). The lung ultrasound score (LUS) was recorded before the patients entered the operating room (T1), 30 min after extubation at the end of anesthesia (T2), and at postoperative 24 h (T3) and 48 h (T4). Venous blood samples were collected to measure the levels of serum clara cell secretory proteins (CC16). The radial artery blood samples were taken for blood gas analysis to calculate the oxygen index (OI). Dynamic lung compliance (Cdyn) was calculated 10 min after intubation (t1) and 10 min before the end of surgery (t2). The total number of lung re‑expansion, the entire duration of lung re‑expansion, the number of lung re‑expansion in which the blood pressure dropped by more than 20% compared with that in the preoperative period, the time of operation, the time of endotracheal extubation (from the end of operation to endotracheal extubation), the fluid intake and output, and the incidence of postoperative pulmonary complication (PPC) on postoperative day two and postoperative day five were recorded. Results Patients in both groups showed elevated LUS at T2−T3 compared with those at T1 (P<0.05). In group R, LUS was elevated at T4 compared with that at T1 (P<0.05). In group LUS‑R, no statistical difference was found in LUS between T4 and T1 (P>0.05). Compared with group R, group LUS showed decreases in LUS at T2−T4 (P<0.05). Patients in both groups presented reduced OI at T2 and T3, compared with those at T1 (P<0.05), and no statistical difference was found in OI between T4 and T1 (P>0.05). Compared with group R, group LUS‑R showed decreases in OI increased at T2, T3, and T4 (P<0.05). Patients in both groups presented reduced Cdyn at t2, compared with those at t1 (P<0.05). Compared with group R, group LUS‑R showed increases in Cdyn at t2 (P<0.05). Patients in both groups presented increased levels of serum CC16 at T2−T4, Compared with those at T1 (P<0.05). Compared with group R, group LUS‑R showed decrease in CC16 levels at T2−T4 (P<0.05). Group LUS⁃R presented decreases in the entire duration of lung re‑expansion, and the number of lung re‑expansion in which the blood pressure dropped by more than 20% compared with that in the preoperative period, compared with group R (P<0.05). There was no statistical difference in the total number of lung re‑expansion, the time of operation, the time of endotracheal extubation, and the fluid intake and output between the two groups (P>0.05). The incidences of PPC on postoperative day two and day five 5 were not statistically different (P>0.05), but a lower incidence was seen in group LUS‑R than that in group R. Conclusions For elderly patients undergoing laparoscopic gastric cancer surgery, pulmonary ultrasound‑guided lung re‑expansion can improve pulmonary oxygenation, increase Cdyn, and reduce the incidence of PPC.