Abstract: The incidence and mortality of chronic obstructive pulmonary disease (COPD) and lung cancer are increasing year by year, which are causing massive social and financial burdens around the world. An increasing number of investigations indicate the possibility of COPD transforming into lung cancer. The pathogenesis of these two diseases have some common aspects, such as epithelial-mesenchymal transition, chronic inflammation, DNA damage, impaired immune system, oxidative stress and tumor angiogenesis, which are heavily complicated. This review summarizes the epidemiological connection between COPD and lung cancer, the molecular-level transformation mechanism as well as the therapeutic strategy. Exploring the transformation mechanism and related signaling pathway of COPD to lung cancer can contribute to block the risk factors for the transformation and provide guidance for the novel drug development and drug therapy.