The incidence of adenocarcinomas of the esophagogastric junction (AEJ) has increased rapidly during the past decades. By the Siewert classification, the AEJ is the tumor center located 5 cm above the anatomic cardia and 5 cm below it, which is divided into three individual subtypes. Complete tumor resection is the primary therapy strategies for tumors of the AEJ. The Japan Clinical Oncology Group 9502 (JCOG 9502) found that transabdominal or transhiatal approach gastrectomy has better survival outcomes compared with left thoracoabdominal approach surgery for Siewert II/III tumors. Transabdominal approach gastrectomy is recommended as the standard treatment strategy for Siewert II/III tumors by the guidelines of the Japanese Gastric Cancer Association (JGCA). However, the length of the proximal resection margin for Siewert-II/III tumors by transabdominal/transhiatal gastrectomy is still controversies. Previous study found that longer than 2cm proximal resection margin had better survival outcome than less than 2cm proximal resection margin for Siewert-II/III tumors. On the other sides, due to more advanced tumor stage of patients in China when compared with Japan and Korea. It is necessary to conduct a randomized control study to analyze the length of resection margin in advanced adenocarcinomas of esophagogastric junction.