This article discusses the meaning of the under-determination thesis raised by the scientific anti-realists,and takes the under-determinative problems in space-time theories and the reply of space-time realists for examples,analyzes deeply the new features of the defense to scientific realism.All these work are based on the semantical analysis,epistemological analysis and the ontological analysis of scientific realism.It indicates that the existence of under-determination thesis has certain grounds,and realists are trying to give a reasonable reply so that they can get out of dilemma of traditional scientific realism.This kind of reply has the feature of contextual realism.
