ObjectiveTo evaluate the clinical efficacy of pre-procedure simethicone on detection of pharynx by upper gastrointestinal endoscopy. MethodsA total of 100 patients with esophageal squamous cell carcinomas （ESCCs） were enrolled in this prospective controlled trial and randomly assigned into two groups. The study group was given gargle with 5 mL simethicone plus 5 mL water combined with conventional procedure before gastroscopy. The control group was prepared according to the conventional procedure. The age, gender, tumor stage， lesion size， doctor's satisfaction and examination time between two groups were analyzed. ResultsThe basic conditions between the two groups， including age， gender， and tumor stage were not significantly different （all P＞0.05）. The detection rate of superficial lesion in pharynx was higher in the study group than that in the control group， with no significant difference ［8.16％ （4／49） VS 2.04％ （1／49）， P=0.362］. The median time of pharyngeal observation in the study group was less than that in the control group （21.7 s VS 33.9 s， P=0.000）. The doctor was more satisfied in the study group than the control group （P=0.001）. ConclusionPre-procedure with simethicone improves the endoscopic visibility and detection rate of superficial squamous cell carcinoma with less observation time.