Interleukin(IL),generated by immunocytes or non-immune cells,is a group of cell factors that holds many important biological effects. Up to now,with the rapid progress of molecular biology and cell biology technique,29 types(IL-1 ～ IL-29)of IL have been reported since its denomination in 1979. IL-23,one kind of interleukin found in 2000,is composed of p19 and p40 sub group. Recent studies showed that it has various biological functions,such as acting on T cell to make it produce various cell factors,acting on DC and MP to affect the secretion of the relevance cell factors. The biological functions of IL-23 have played an important role in various diseases. This review describes the molecular structure,biological function,and its effects on related diseases.