OX40 (CD134; TNFSF4) is a member of the TNF superfamily and is a type I transmembrane glycoprotein. Human OX40 is composed of a 28aa signal peptide, an 185aa extracellular domain, a 20aa transmembrane domain, and a 41aa cytoplasmic domain. The human OX40 ligand (OX40L/CD134L) contains 183 amino acids (139 extracellular amino acids, 21 transmembrane amino acids, and 23 intracellular amino acids) and is a member of the TNF family. It is a type II transmembrane glycoprotein. OX40/0X40L is an important pair of co stimulatory molecules that play an important role in the immune response of the body and various diseases. Immunotherapy by intervening in their interactions has achieved excellent therapeutic effects in many animal models, providing a theoretical and experimental basis for future clinical treatment.