Objective To explore the relationship between diaphragm function and postoperative pulmonary complications and short-term prognosis，analyze the risk factors leading to diaphragm dysfunction, so as to guide the formulation of perioperative strategies to promote rehabilitation for post-pneumonectomy patients.Methods Ninety patients of unilateral pneumonectomy in thoracic surgery of our hospital were collected sequentially. Diaphragmatic excursion was measured sequentially for each patient before and 24 hours，48 hours，and 72 hours after operation by beside ultrasound. According to the postoperative diaphragmatic excursion，the patients were divided into two groups：diaphragm dysfunction group（DD） and Normal diaphragmatic functin group（ND）. The differences in the incidence of postoperative pulmonary complications and short-term prognosis between the two groups were compared. Logistic regression was used to analysis risk factors which led to diaphragm dysfunction.Results The incidence of postoperative pulmonary complications（atelectasis，postoperative residual cavity，pleural effusion，and lung infection） in the DD group was higher than that in the ND group，and the differences were statistically significant（all p＜0.05）；The short-term prognosis of the DD group （the time to complete lung recruitment and post-operative catheterization） was worse than that of the ND group，the difference was statistically significant（all p＜0.05）. In both grops, diaphragmatic excursion first decreased and then increased on the operative side，while it remained unchanged on the opposite side at 48 hours after operation and increased compensatively from 72 hours after operation；Logistic regression analysis showed that smoking history and lobectomy were risk factors for postoperative diaphragmatic dysfunction（P＜0.05）.Conclusion Diaphragmatic dysfunction after pneumonectomy leads to higher incidence of pulmonary complications， which is not conducive to short-term prognosis. Bedside ultrasound can be used to evaluate the diaphragmatic excursion during peri-operative period，and early detection of diaphragm dysfunction can provide help for clinical development of corresponding strategies.