In the research of contextualism, how to ascertain the boundaries of the context is the most specific problem and, however, the blurriest problem as well. This article tries to explore the boundaries of the context and to present their internal meaning in the "contextualizing move" which was launched from 1980s. The ascertainment of the boundaries is held from three aspects: the syntactic boundary, the semantic boundary and the pragmatic boundary. This differentiation can effectively offers some meaningful perspectives and trains of thought for the contextual analysis method, so the methodology of contextual analysis will be strengthened for its position and effect in scientific explanation.