Once a patient with lung cancer develops pericardial effusion, he or she has advanced lung cancer, which is also known as stage IV lung cancer. For advanced or stage IV lung cancer, the main treatment at present is systemic treatment. For a large amount of pericardial effusion, it is mainly based on pericardial effusion puncture and drainage, together with systemic chemotherapy, targeted therapy or immune checkpoint inhibitor therapy, etc. However, it mainly depends on the specific pathological type of lung cancer, such as small cell lung cancer, chemotherapy is the main treatment, while in case of lung adenocarcinoma with genetic mutation, targeted drugs such as gefitinib, erlotinib or crizotinib can be used. If there is no genetic mutation, immune checkpoint inhibitors, such as pablizumab, can be used. In conclusion, once lung cancer patients develop pericardial effusion, they have advanced lung cancer, which is a very poor prognosis.