Abstract: Gene editing technology can artificially modify genetic material at target sites by inserting, deleting or replacing them precisely in genomic DNA. The development of the clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9 (CRISPR/ Cas9) system in recent years has greatly improved researchers,s ability to edit the genomes of various cells. However, due to the low efficiency of homologous directed repair (HDR), many approaches to improve precise gene knock-in efficiency based on the CRISPR/Cas9 system have been developed by inhibiting non-homologous end joining (NHEJ) or enhancing HDR, including chemical regulation, synchronous expression, and homologous arm optimization. Here, this review focuses on recent advances in how these methods can optimize Cas9 knock-in efficiency.