Abstract: Objective:The purpose of this study was attempted to investigate the direct effects of various non-steroid antiinflammatory drugs （NSAIDs） at low concentration equivalent to serum level at normal oral dosage on intracellular calcium ion in human knee articular chondrocytes in vitro.Methods:After the chondrocytes were cultured for 3 days, the instant change of average fluorescent intensity （AFI） within chondrocytes stained by Fluo-3/AM （cacium fluorescence probe） under the treatment of high and low concentration of NSAIDs （aspirin, sulindac,indomethacin and diclofenac sodium） was detected with laser scanning confocal microscope. Results:The AFI was significantly decreased with rapid speed under the high concentration of all NSAIDs tested compared to that of normal saline in control （P＜0.001,n=6）. At the low concentration, however, diclofenac sodium had a minimum influence on intracellular AFI compared with sulindac, aspirin and indomethacin. Conclusion:These observations suggest normal human chondrocytes respond differently to various NSAIDs. Each drug may exhibit unique attributes with respect to instant efficacy on free calcium within chondrocytes. In addition, diclofenac sodium probably induces less damage on the normal chondrocytes than others.