The inappropriate expression of miRNAs have been found in many kinds of complex diseases, such as cancers, cardiovascular diseases, metabolic diseases, inflammatory diseases and so on. Many studies have demonstrated that bioactive small molecules (or drugs) can regulate the miRNA expression, which indicate that targeting miRNAs with small molecules is a new type of therapy for human diseases. SM2miR is a manual curated database which collects and incorporates the experimentally validated small molecules' effects on miRNA expression in 21 species from the published papers. Each entry contains the detailed information about small molecules, miRNAs and their relationships, including species, small molecule name, DrugBank Accession number, PubChem CID, approved by FDA or not, miRNA name, miRBase Accession number, expression pattern of miRNA, experimental detection method, tissues or conditions for detection, evidences in the reference, PubMed ID and the published year of the reference.