Objective To evaluate the clinical significance of operative indication in patients with lung cancer accompanied by lung dysfunction using cardiopulmonary exercise test (CPET). Methods Before operation, using CPET with step program, work rate(W%), maximal oxygen uptake(VO2%P), maximal oxygen uptake per kilogram(VO2/kg) and other indexes were tested in the end of load exercise in 195 patients with lung cancer accompanied by lung dysfunction. Chi-square test and logistic regression analysis were performed for the abnormal rate of indexes mentioned above in patients with or without postoperative respiratory failure. Results After pneumonectomy, W%,VO2%P, VO2/kg, metabolic equivalent (MET), minute ventilation(VE) and respiratory frequency(BF) in patients with postoperative respiratory failure were lower than those in patients with non-postoperative respiratory failure (Plt;0.05 or 0.01). Logistic regression analysis showed that VElt;30 L/min and (BFlt;30) times/min were more related to the morbidity of postoperative respiratory failure than other indexes. As for the patients with lung dysfunction treated by lobectomy, this indexes didn’t show any significant difference between patients with or without postoperative respiratory failure. However, this indexes decreased in patients with postoperative respiratory failure whose ratio of forced expiratory volume in one second to forced vital capacity (FEV1%) were lower than 60%(Plt;0.05 or 0.01). Logistic regression analysis showed that VO2%Plt;60% related to the morbidity of postoperative respiratory failure. Conclusion CPET is useful to evaluate the operative indication in patients with lung cancer accompanied by lung dysfunction. VO2%Plt;60% should be selected as a evaluating index.