Objective To study the effect of interleukin (IL)-1β on mitochondria of chondrocytes and reactive oxygen species.Methods Rat chondrocytes were isolated and cultured in vitro,10 ng/ml IL-1β was added for establishing model of osteoarthritis.Then,ratio of apoptosis was surveyed by Annexin V-FITC and PI flow-cytometry.After Hoechst 33342 dyeing,morphology of nucleus was observed by fluorescence microscope.After rhodamine-123 luorescent staining applied,change of mitochondria membrane potential was observed by confocal microscopy.We evaluated the ability of ATP synthesizing in mitochondria by luciferase reaction.Content of active oxygen was observed by confocal microscopy.T test was used for statistical analysis.Results IL-1β could obviously reduce the mitochondrial membrane potential of chondrocytes and its ability to synthesize ATP,and could promote the expression of reactive oxygen species in cells.The values were changed to (24±4) U,(4.1±0.8) pmol/106 cells and (89±7) U from (86±10) U,(13.3±3.0) pmol/106 cells and (17±3) U.The difference had statistical significance.Conclusion IL-1β can induce chondrocyte differentiation by destroying the mitochondrial membrane integrity of chondrocytes and promoting the expression of reactive oxygen species.It can also promote the articular cartilage degeneration.