Clinical practice showed that some advanced gastric cancer (AGC) patients achieved long-term survival after surgery, whereas some benefited from non-surgical treatment. In recent years, with the emergence of new drugs, diversity of treatment and development of multi-disciplinary team, the concept of conversion therapy comes into attention. Owing to diverse phenotypes with scattered cases, publications are mainly case reports or small sample studies from single centers, which makes it hard to acquire high-level evidence. On illustrating the definitions of AGC and conversion therapy, as well as integrating peritoneal metastasis, liver metastasis, No.16 lymph nodes metastasis, cytology positive and organs infiltration (T4b), we tried to classify AGC as resectable IIII( and unresectable IIII(. Resectable IIII( refers to lesions that could be resected as R0 evaluated by present diagnostic modalities, conditions of patients and therapeutic management, in which it is further classified as low-risk and high-risk subtypes, according to operation risk. If R0 is not achieved with the evaluation as above, it is classified as unresectable IIII(, in which it is further classified as conversed, partly conversed and non-conversed types after systemic therapy. For AGC patients with unresectable IIII(, operation must be performed more carefully, and the making of treatment protocols, the judge of operational time and the choice of operation procedure should be based on multi-disciplinary team. Such classification is aimed to facilitate clinical application and launch clinical trials, better to explore the characteristics of AGC.