Abstract: The RAS (rat sarcoma) gene is one of the important oncogenes, and its mutation is present in about 30% human tumors. KRAS (kirsten rat sarcoma viral oncogene) is one of the three RAS subtypes, and KRAS mutations are more common than the mutations in other two RAS subtypes. In recent years, with the continuous research, new ideas have been provided for the treatment of cancers via targeting-KRAS. Efforts have been made to develop various KRAS inhibitors. Here, based on the mechanism of action, we classified KRAS inhibitors into two categories: inhibitors that directly target KRAS and inhibitors that indirectly act on KRAS. The representative KRAS inhibitors were summarized and introduced in this paper.