Background and Aims: Hepatitis B virus immune escape gives a challenge to prevention,diagnoses and treatment to hepatitis B.The aim of this study was to explore characteristics and its molecular mechanism of HBV immune escape in HBV endemic area.Methods: HBV isolates from 210 patients with coexistence of HBsAg/HBsAb were sequenced for HBsAg major hydrophilic region (MHR) analysis.In vitro biological functional analysis including antigenicity and secretion ability was conducted to study influence of N-glycosylation mutations on viral fitness after identification of N-glycosylation conformation.