Abstract: Metagenomics is a new emerging field which had been developed in recent years. The main technique comprises isolation DNA from environment directly, gene library construction and screening of target gene clone. Metagenomics can overcome the shortages of traditional culturing methods and it is an important new way to study non-culturable microbes, to find new functional genes, and to access new. In recent years, metagenomics has been widely applied in many fields and in-deep research was conducted in medicine, agriculture, energy development, environmental restoration, bio-technology, bio-defense， and so on. The article reviewed the main techniques and research progress of metagenomics briefly.

Key words: metagenomics; library construcion; library screening; research progress