Abstract: The classic liver S4 segment resection is a typical structural resection procedure, but it often overlooks the detailed anatomy of this liver segment. The hepatic pedicle (G4) of S4 segment of liver is entirely derived from the left hepatic pedicle. The authors start with the anato-mical characteristics of left hepatic pedicle, analyze the quantity and distribution characteristics of G4 from the perspective of portal vein. Based on analysis of the anatomical characteristics and course of umbilical fissure vein, the authors expound the new viewpoint on the true anatomical range of S4 segment of liver. The application of the new approach of lowering the umbilical plate in the anato-mical resection of S4 segment of liver, the authors discuss the precise location and opening method of the umbilical fissure. In addition, based on the internal structural characteristics of left hepatic pedicle, the authors analyze the common causes and coping strategies of bile leakage complications during liver S4 segment resection.