Currently, the number one cause of cancer deaths worldwide is lung cancer. Although the cause is not completely clear, lung cancer is highly related to smoking, atmospheric pollution (e.g. benzo(a)pyrene), occupational exposure (e.g. mineral dust), chronic inflammation, etc., especially the association with smoking is extremely high. The number of smokers in China is quite large, and tobacco control efforts have had little effect, so lung cancer has become a major problem in front of us. If lung cancer spreads to other important organs such as brain or liver, it can cause dysfunction of these organs, and if the important organs of human body are damaged too much, it will be difficult to maintain normal life and even life-threatening. If it metastasizes to bones, it can cause severe bone pain and pathological fracture. It can be seen that the later lung cancer is detected, the greater the harm will be, and then treatment will be half-hearted and ineffective. However, this is not easy to achieve. Because lung cancer does not have any special symptoms in early stage, but only symptoms common to general respiratory diseases, such as cough, sputum and blood, low fever, chest pain and tightness, which can be easily ignored. The recognized gold standard for lung cancer diagnosis, puncture biopsy, is harmful to the body and can only be done when lung cancer is highly suspected, and it is not possible to check it anytime and often.