Most people want to be able to read their reading materials quicker and remember them effectively. Covering a large quantity of reading materials at a normal speed requires much more time than is usually available. Good readers, however, can cover a lot of materials by identifying key elements of a sentence for key idea with the help of connectives when skimming. Constructivism theory emphasizes that students need to actively construct the meaning of their knowledge they have learned, and actively explore and discover knowledge. Syntax is the core of the whole language system with syntactic structure occupying a macroscopic and important position in improving students' language ability and language level in a real sense. This paper introduces and analyzes how to identify key elements of a sentence for key idea with the help of connectives under constructivism so as to find a practical and feasible reading strategy when skimming. It is advised that readers glance at secondary sentences by reading the connectives as they are helpful in getting possible additional information while successfully identifying key elements of a sentence for key idea. The method fundamentally helps students improve their reading speed and develop their skimming understanding ability. The research methods of this paper are the ones of experience, literature review, theoretical basis, the main language order and keen analysis. This paper concludes by understanding the method of identifying key elements of a sentence for key idea with the help of connectives in skimming practice when reading under constructivism theory and its role is to guide readers to apply the knowledge of subject-predicate-object grammatical rule as the main language order in the skimming practice to help readers to get the general meaning of a sentence, paragraph, passage and a text.