Abstract: Bromodomain and extra-terminal (BET) family, a class of proteins that can specifically recognize acetylated lysine and regulate gene transcription, play an important role in the occurrence and development of diverse diseases. Bromodomain-containing protein 4 (BRD4), a member of the BET family, can combine with acetylated histones or non-histones, thereby regulating gene replication and transcription, and affecting the cell cycle, cell differentiation and signal transduction. The up-regulation of BRD4 expression is closely related to the malignant development of various tumors. Inhibition or degradation of BRD4 can effectively control the malignant progression and distant metastasis of tumors. Therefore, BRD4 is a promising tumor epigenetic target. In recent years, small-molecule inhibitors and degraders for BRD4 have received extensive attention and research, and have shown good anti-tumor effects used either alone or in combination with other antitumor drugs. The structural characteristics, biological functions and research progress of small molecule inhibitors and degraders of BRD4 are reviewed, in order to provide reference for the development of new inhibitors and degraders of BRD4.