The Nobel Prize in Chemistry 2020 was awarded jointly to Emmanuelle Charpentier and Jennifer A. Doudna "for the development of CRISPR genome editing tool." They have discovered the sharpest tools for gene editing: the CRISPR/Cas9 genetic scissors, which have revolutionary impact on life sciences. The CRISPR system is an adaptive immune system in prokaryotes. Cas9, an effector protein of type II CRISPR-Cas system, functions as a dual-RNA-guided DNA endonuclease, which is able to cleave any dsDNA generating dsDNA break. The CRISPR-Cas9 has been widely used in gene editing, due to its simplicity, high efficiency and low price. This paper introduces the research findings of 2020 Chemistry Nobel Prize winners, summarized the discovery process of CRISPR system and the activity and application of CRISPR-Cas9.