Objective To prevent bile duct injury, a new anatomy marker, named “common bile duct window” is created. Methods From November 2005 to March 2006, 60 patients who underwent laparoscopic cholecystectomy were researched in this hospital. All data were collected, including: age, gender, course of disease, body mass index (BMI), blood lipid level (triglyceride and cholesterol), the thickness of gallbladder wall and the degree of cholecystitis. The frequency, location and mean size of “common bile duct window” were recorded and calculated. Patients were divided into two groups according to the presence of “common bile duct window”, and the diference of data between two groups was analyzed by using χ2 test or t test. Results “Common bile duct window” was found at the end of hepatoduoduenal ligament with oval-shaped, the mean longitude of “common bile duct window” was (1.20±0.60) cm, and mean width was (0.45±0.30) cm. “Common bile duct window” were found in 81.6% (49/60) of patients. Age, gender, course of disease, BMI, triglyceride and cholesterol were proved to have no relationship with the presence of “common bile duct window” （Pgt;0.05）, but the thickness of gallbladder wall and the degree of cholecystitis affected the presence （P＜0.05）. Conclusion An oval-shaped “common bile duct window” can be found in almost all patients undergoing laparoscopic cholecystectomy. During the operation, the common bile duct can be located easily by the surgeon through “common bile duct window”, thereby to avoid common bile duct injury when the cyst duct was dissected. It is believed that during laparoscopic cholecystectomy the chances of bile duct injuries can be effectively decreased by the presence of “common bile duct window”.