Phylum Chloroflexi is a deep branching lineage of the domain Bacteria. Members of the phylum are widely distributed in different habitats of the biosphere. The validly published microbes in the phylum include 9 classes of only 56 species. The results based on molecular ecology imply the majority members of this phylum are still uncultured. Chloroflexi microbes are diverse in morphology, nutrition, metabolic pathways, and play important roles in biogeochemical cycles of multiple elements including carbon, nitrogen and sulfur. Study on Chloroflexi may contribute to understanding microbial diversity, metabolic characteristics and ecological processes in the environment, it is important in clarifying the adaptation of microorganisms to the environment and their evolution. In this paper, the discovery history, nutrition, metabolism and the role in the elemental cycling of Chloroflexi are summarized. Isolation methods and potential application values are also reviewed. Expectations for Chloroflexi cultivation, evolution and geochemical cycling are also indicated.