Innate immune system is the first line of defense for microorganisms to invade the host, which is very important for the survival and health of human body. Antimicrobial peptide (AMP) is one of the important component of human innate immunity. LL-37 is the only AMP of the Cathelicidins family in humans, it is an amphiphilic helical peptide composed of 37 amino acid residues and has been proven to have broad-spectrum antimicrobial activity. This article focuses on summarizing the antimicrobial and immunomodulatory activities of LL-37, as well as the research progress of bacterial and fungal resistance to it.