Abstract: Bromodomain and extraterminal (BET) proteins are a class of proteins that can interpret epigenetic codes and play an important role in regulating gene transcription through identifying and binding acetylated histones or non-histones proteins. The BET inhibitors have emerged with good therapeutic effects in preclinical disease models such as cancer and inflammation. Some of them have entered clinical studies, demonstrating that there is considerable prospect for drug development with BET as a potential therapeutic target. This review briefly describes the structures and functions of the BET proteins, the BET inhibitors in various diseases, as well as molecular mechanisms involved.