The development of recombinant DNA technology in the 1970s marked the beginning of a new era for biology. For the first time, molecular biologists gained the ability to manipulate DNA molecules, making it possible to develop novel medicine. Nowadays, the introduction of targeted genomic sequence changes into living cells and organisms has become a powerful tool for biological research and provided a potential avenue for therapy of genetic diseases. Of these new technologies, the most exciting is CRISPR/Cas9, a gene editing system adopted from bacterial immune system that is efficient, rapid, and easy-to-use. CRISPR/Cas9 technology allows targeted knock-in and knock-out and/or changes of any gene within the genome. In this study, this technology and its applications in treatment of genetic disease was discussed.