In the clinic, keratin 21-1 is usually used for the auxiliary diagnosis of lung cancer. Keratin 21-1 is generally not able to be regulated, and timely consultation is needed to improve the relevant examinations and then carry out targeted treatment. Keratin 21-1 is a commonly used tumor marker, and its elevation mostly suggests the possibility of lung cancer, and the positive rate of elevated keratin 21-1 in lung cancer patients can reach about 64%. However, a simple increase in Keratin 21-1 does not necessarily mean that the patient has lung cancer, and a diagnosis of cancer requires a comprehensive examination and evaluation, such as the detection of a mass on CT of the lungs, and a combination of clinical symptoms and auxiliary examinations. When the keratin 21-1 is found to be elevated, it is necessary to go to the hospital in time to avoid delaying the disease.