Objective To compare the effects of selenium nanoparticles (Nano-Se) and sodium selenium (Na2SeO3) on apoptosis and reactive oxygen species (ROS) of articular chondrocytes from patients with Kashin-Beck Disease (KBD) in vitro,and provide a scientific basis for preventing KBD.Methods The subjects with KBD were diagnosed on National Clinical Diagnostic Criteria of KBD (WS/T207-2010),articular cartilage from 8 patients undertaken joint replacement operation were collected.In vitro,chondrocytes were treated with concentration of 0,25,50,100,200,300,400 and 500 μg/L of Nano-Se and Na2SeO3 for 5 d,respectively.Cell growth was detected by MTT assay,and the highest concentration and time corresponding to the highest survival rate of Nano-Se and Na2SeO3 were used in the following experiment.KBD chondrocytes were treated with Nano-Se and Na2SeO3,and divided into control group,Na2SeO3 group,Nano-Se group according to the randomized design.Each group had 8 cases.The cell apoptosis and ROS were detected by flow cytometry.Results The optimal intervention concentration of Nano-Se and Na2SeO3 was 100 and 400 μg/L,respectively.The optimal intervention time of NanoSe and Na2SeO3 both was 3 days.There was a significant decrease in the total and terminal apoptosis,ROS level of chondrocytes in Nano-Se group [(4.67 ± 0.89)％,(1.51 ± 0.48)％,(56.04 ± 4.81)％] and Na2SeO3 group [(7.07 ±0.25)％,(4.37 ± 0.37)％,(87.13 ± 6.60)％] compared with those of control group [(9.95 ± 0.38)％,(6.93 ± 0.42)％,(125.17 ± 16.60)％,all P ＜ 0.01].The difference of early apoptotic rate among control group,Na2SeO3 group,NanoSe group [(3.02 ± 0.41)％,(2.7 ± 0.46)％,(3.16 ± 0.56)％] was not statistically significant (F =2.11,P =0.35).Conclusion Appropriate concentration of Nano-Se can significantly decrease oxidative stress of KBD chondrocytes and inhibit apoptosis compared to Na2SeO3.