The present invention relates to a benzimidazole derivative, a preparation method therefor and the medical use thereof. In particular, the present invention relates to a benzimidazole derivative as shown in formula (I), a preparation method therefor and a pharmaceutically acceptable salt thereof and the use of same as a therapeutic agent, especially as a bromodomain protein inhibitor, wherein the definition of each substituent in formula (I) is the same as the definition in the description.