Life expectancy of stage IV lung cancer is mostly in 0.5-1.5 years, but there is no way to determine the exact time. Patients with stage IV lung cancer already have metastases in liver, bone and brain tissues, clinically most of the patients’ life expectancy is around 0.5-1.5 years, but there is no way to determine the specific time, which mainly needs to depend on the patient’s treatment effect and other conditions. If there is only a single bone metastasis in stage IV lung cancer and the bone damage is not very serious, timely radiotherapy, chemotherapy and bisphosphonate treatment can control the disease well and prolong the patient’s life to more than 3 years. In addition, if there is targeted drug therapy, the treatment time can be extended to 5 years or even longer.