Objective To study the effect of preoperative frailty on postoperative complications in elderly patients after lung cancer surgery. Methods This prospective cohort study included 400 patientswho aged ≥ 60 years， ASA gradeⅠ-Ⅲ and scheduled to undergo thoracoscopic lung cancer surgery. According to the 28-item frailty scale， the patients were divided into non-frailty group （Group A），pre-frailty group （Group B）and frailty group （Group C）. The primary outcome was the incidence of postoperative complications within 30 days. Results A total of 334 patients were included for data analysis. The median age of the patients was 65 years oldand the incidence of frailty was 35.3%. The incidence of postoperative complications was 20% in group A，36.7% in group B，and 52.5% in group C，which was significant difference among the three groups （P = 0.003）.Multivariate regression analysis showed that frailtystatus，Charlson Comorbidity Index，ASA，pathological stage and duration of surgery were independent risk factors for postoperative complications.After adjusting all risk variables，the incidence of postoperative complications in frail patients was higher than that in non-frail patients （OR=2.987，95%CI：1.496~ 3.979），and the incidence of pre-frail patients was also higher than that in non-frail patients （OR = 1.792， 95%CI：1.554 ~ 2.826）. Conclusion Preoperative frailty can increase the incidence of postoperative complications and prolong the length of hospital stay in elderly patients with lung cancer surgery.