Cancer remains a leading cause of death worldwide. Ten million deaths were caused by cancer in 2020, accounting for 1/6 of the total deaths (Sung et al., 2021). In most types of cancer, genes are usually altered infrequently (Prasad, 2016). In contrast, epigenetic alterations far exceed somatic mutations in almost all cancer types (Witte, Plass, & Gerhauser, 2014). Epigenetic alterations are methods of modification that do not necessarily permanently alter genes (Ilango, Paital, Jayachandran, Padma, & Nirmaladevi, 2020). It is derived from small chemical compounds in DNA or chromosomal proteins and is essential for cells to control and regulate gene activity (Miranda Furtado et al., 2019). Epigenetic alterations include DNA modification, RNA modification, histone modification, non-coding RNAs and chromatin structure remodeling, etc. (Jung, Hernández-Illán, Moreira, Balaguer, & Goel, 2020). DNA and histones regulate epigenetic modification through three kinds of epigenetic proteins: writer, reader, and eraser. Writers alter the existing state by adding epigenetic marks. Readers only respond to specific epigenetic marks. On the other hand, Erasers induce changes by removing epigenetic marks (Peixoto, Cartron, Serandour, & Hervouet, 2020). Because epigenetics are reversible, drugs targeting epigenetics provide new directions and targets for tumor treatment. Currently, common medicines include DNA methyltransferase inhibitors and histone deacetylase inhibitors. In addition, the combined application of epigenetic drugs and multiple anti-tumor drugs also has broad application prospects. This article introduces the regulatory mechanism of epigenetics, reviews the development and clinical achievements of epigenetic drugs, and looks forward to the future design direction of related drugs.