Objective To investigate the phenotypic change and proliferation of fibroblasts in human inflammatory strictured bile duct wall. Methods We observed the density and ultrastructure of fibroblasts, and the histologic structure in human normal bile duct wall and inflammatory strictured bile duct wall by light and electron microscope.Results The results showed that fibroblasts were the main source of extracellular matrix production in bile duct wall. The phenotype of fibroblasts in inflammatory strictured bile duct wall changed obviously, quiescent fibroblasts were activated and transformed to myofibroblasts, with massive proliferation. Conclusion These data suggest that massive proliferation of activated fibroblasts and myofibroblasts is the main source of extracellular matrix overproduction which results in inflammatory bile duct stricture.