Abstract: Lung cancer is the leading cause of deaths from all cancers worldwide. TNM staging system can describe the information of the growth and spread of lung cancer, and it also plays a very important role in guiding the clinical treatment. The 7th edition of the TNM staging of lung cancer being widely used in worldwide was published by the Union for International Cancer Control (UICC) and American Joint Committee on Cancer (AJCC) in 2009. However, with the development of treatment for lung cancer, prognosis of lung cancer after the treatment would be significantly changed, and the 7th edition staging may be difficult to meet current clinical needs. Therefore, the International Association for the Study of Lung Cancer (IASLC) started a research to establish objectives for the T, the N, and the M components to inform the 8th edition of the TNM classification of lung cancer in 2014. Despite the large number of patients, not all descriptors could be validated. This prompted a new collection of retrospective and prospective data to overcome the limitations of the original retrospective database. The new IASLC database has information on 94 708 new patients diagnosed of lung cancer between 1999 and 2010. After analysis of the new database, IASLC formed the basis of recommendations to the UICC and AJCC for the revision of the 7th edition of TNM classification of lung cancer. They published the revised version of the 8th edition of TNM classification of lung cancer in 2015. This article would like to try to interpret this revision in details.