Recently, the incidence and detection rates of multiple primary lung cancer (MPLC) are increasing. The diagnosis of MPLC depends mainly on the Martini-Melamed criterion and ACCP criterion at present, taking all features (histological, genetic, radiologic and clinical) into account. It may be easy to diagnose cases of MPLC that exhibit different histological types, but it is difficult to diagnose cases that exhibit similar histological type. DNA polity, gene mutations, microsatellite alteration and so on provide new methods for the accurate diagnosis of MPLC. They can evaluate the clonal relationship and help differential diagnosis between MPLC and metastasis. The first therapeutic choice for MPLC is curative operation. The surgical approach includes lobectomy, wedge resection and segmentectomy. For those which cannot be resected, we can synthesize chemotherapy, radiotherapy, stereotactic ablative radiotherapy (SABR), radiofrequency ablation (RFA), molecular targeted therapy, etc.