Retrospective clinical case studies in recent years have shown that most cases of lung cancer and abdominal aortic aneurysm (AAA) are detected at the same time and that there is a wide variation in the prevalence of AAA in patients with primary lung cancer reported in the literature, with some papers suggesting as high as 11%, suggesting that there may be a relationship between the prevalence of the two diseases. However, its exact incidence and mechanism are unknown. Accurate prevention of AAA in patients with primary lung cancer requires more in-depth studies. To solve the above problems, a multi-center prospective epidemiological investigation and mechanism study on the association of AAA in primary lung cancer combined has become particularly urgent. The results of the study will be of great significance for the follow-up treatment and prognosis of lung cancer patients as well as the improvement of long-term survival rate of lung cancer patients, and will also provide scientific basis and clinical guidance for the screening and prevention of AAA in lung cancer patients.