In the early 20th century Hong Kong has accepted a large number of immigrants; some of them experienced the identity change from immigrant to fishermen, and finally to fishermen Christian. At the same time, for their inner part, they suffered the transformation of self-identity. When passing through all aspects of the whole process - the anxiety, reflection, looking for identity, cultural selection and group identity - they ultimately turned to the Christian identity of the self-identity from folk religions believers. This paper aims to interpret the changed and the reserved among Hong Kong Fishermen’s Christian self-identity building through Giddens’ self-identity theory. In the context of modernity, wandering individuals driven by internal reflection, kept self-identity in the change process, during which the continuity of “ontological security” ran through as permanent constitute of self-identity . This article is divided into five parts. The first part is the literature review and theoretical interpretation; the second part is an introduction of research methods and the object of study; the third part, based on the interaction between family, Gospel, and Church, tries to explain the fishermen Christian self-identity’s “constant” in the transition; the fourth part illustrates the process of self-identity change at the cultural level, aiming at the interpretation of self-identity’s change. And the fifth part is the conclusion.