The clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated(Cas) protein 9 system(CRISPR/Cas9) provides a powerful tool for targeted genetic editing. Directed by programmable sequence-specific RNAs,this system introduces cleavage and double-stranded breaks at target sites precisely. Compared to previously developed targeted nucleases, the CRISPR/Cas9 system demonstrates several promising advantages, including simplicity, high specificity,and efficiency. Several broad genome-editing studies with the CRISPR/Cas9 system in different species in vivo and ex vivo have indicated its strong potential, raising hopes for therapeutic genome editing in clinical settings. Taking advantage of non-homologous end-joining(NHEJ) and homology directed repair(HDR)-mediated DNA repair, several studies have recently reported the use of CRISPR/Cas9 to successfully correct disease-causing alleles ranging from single base mutations to large insertions. In this review, we summarize and discuss recent preclinical studies involving the CRISPR/Cas9-mediated correction of human genetic diseases. The clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated (Cas) protein 9 system (CRISPR / Cas9) provides a powerful tool for targeted genetic editing. Directed by programmable sequence-specific RNAs, this system incorporating cleavage and double-stranded breaks at target sites precisely. Compared to previously developed targeted nucleases, the CRISPR / Cas9 system demonstrates several promising advantages, including simplicity, high specificity, and efficiency. Several broad genome-editing studies with the CRISPR / Cas9 system in different species in vivo and ex vivo have indicated its strong potential, raising hopes for therapeutic genome editing in clinical settings. Taking advantage of non-homologous end-joining (NHEJ) and homology directed repair (HDR) -mediated DNA repair, several studies have recently reported the use of CRISPR / Cas9 to successfully correct disease-causing alleles ranging from single base mutations to large insertions. In this review, we summarize a nd discuss recent preclinical studies involving the CRISPR / Cas9-mediated correction of human genetic diseases.