Surgical operation is the first choice for most patients who suffer from early non-small cell lung cancer. The risk of ordinary thoracic surgery is between intermediate and high risk. Due to the high incidence of postoperative pulmonary complications after thoracic surgery, preoperative cardiopulmonary reserve assessment is extremely necessary and important. In recent years, lots of assessment tools are clinically used, including pulmonary function tests, arterial blood gas analysis, breath-holding test and 6-minute walk test. In addition, cardiopulmonary exercise test is used extensively. This article reviews the current status of preoperative cardiopulmonary reserve assessment in thoracic surgery to guide clinical decisions, reduce postoperative complications and improve outcomes.