Background and Aims Siewert Type Ⅱ adenocarcinoma of the esophagogastric junction (AEG), located at the gastroesophageal junction, has been a subject of controversy regarding the optimal surgical approach due to its unique anatomical location. This study was performed to investigate the value of preoperative endoscopic ultrasound (EUS)-guided titanium clip marking in predicting the surgical approach for Siewert type Ⅱ AEG, so as to provide assistance in developing safe and precise surgical strategies in clinical practice.Methods Using a prospective controlled study design, 60 patients with Siewert type Ⅱ AEG who underwent surgery in the 900th Hospital of the Chinese People's Liberation Army Joint Logistic Support Force from February 2020 to December 2021 were enrolled. The patients were randomly assigned to a study group and a control group, with 30 patients in each group. After standard admission examinations, the patients in the study group underwent determination of the longest infiltrating position of the tumor along its longitudinal axis under EUS-assisted direct visualization, which was positioned by placing two titanium clips at the same height plane 1 cm beyond on the oral side The clip position was immediately confirmed by abdominal X-ray. The patients in the control group did not undergo any marking. The surgical approach for the study group was determined based on the relationship between the titanium clips and the 10th thoracic vertebra, while the surgical approach for the control group was determined based on preoperative routine examinations, such as CT and gastroscopy. Relevant clinical data were compared between the two groups.Results There were no statistically significant differences between the two groups in baseline characteristics, including gender, age, body mass index, smoking history, alcohol history (all P>0.05); there were also no statistically significant differences between the two groups in terms of surgical duration, intraoperative bleeding, tumor diameter, esophageal margin, length of hospital stay, postoperative pathological stage, tumor T stage, and N stage (all P>0.05). The analysis of the concordance between predicted and actual surgical approaches showed a significantly higher rate of concordance in the study group compared to the control group (96.67% vs. 86.21%, P<0.001). The incidence of postoperative complications in the study group and the control group was 26.67% and 30.00%, respectively, with no statistically significant difference (P=0.783).Conclusion Preoperative EUS-guided titanium clip marking is a simple, safe, and highly reliable procedure with practical clinical application value for determining the surgical approach in Siewert type Ⅱ AEG.