Abstract: Objective To determine the influence of location, depth and size of upper gastrointestinal （GI）submucosal tumors (SMTs) on the success of submucosal tunneling endoscopic resection (STER). Methods Patient records of 31 cases with upper GI SMTs who had STER between Jan. 1, 2014 and June 30, 2015 in West China Hospital of Sichuan University were retrieved. The success of STER was determined by its efficiency, complete resection rate, and incidence of complications. Results Of the 31 cases, 29 were treated successfully, with an average of （13.76±9.70） min and （32.00 ±27.35） min for tunnel formation of esophageal and stomach mucosal tumors respectively ( P=0.045). The 2 unsuccessful cases were gastric tumors. SMTs resection for mucous layer and muscularis propria took （17.50±9.06） min and （36.24±15.68） min, respectively ( P=0.004). SMTs resection for tumors diameter <2.0 cm and ≥2.0 cm took （25.78±12.13）min and （39.73±19.23） min, respectively ( P=0.023). Six cases of gastric tumors from muscularis propria had complications (19.4%) during or after surgery. Conclusion Location, depth and size of upper GI SMTs has implications on duration of different STER stages, which may determine complete resection rate and incidence of complications.