Objective To explore the curative effect of ultrasound-guided intra-articular injection of triptolide nanoparticle（TPN） on rabbit antigen-induced knee arthritis and the value of ultrasound in evaluating the curative effect of rabbit arthritis.Methods Twenty seven New Zealand white rabbits were randomly divided into 4 groups after AIA model were induced.The knee joints of TPN group，TP group and BS group were injected intra-articular with TPN，triptolide（TP） and betamethasone（BS） respectively guided by ultrasound，7 rabbits in each group.The control group （other 6 rabbits） were punctured but not injected with any drugs.The ultrasonic scores and pathological changes of joint were assessed in synovitis，synovial blood flow and the bone erosion.Meanwhile the correlation of ultrasonic scores and pathological scores was tested.Results Compared with the control group，the synovitis scores of other groups were lower（P＜0.05）.The ultrasonic synovitis scores of BS group and TPN group（both P＜0.05） were lower than that of TP group，so were the pathological synovitis scores（both P＜0.05）.Compared with the control group，TP group，BS group and TPN group were all effective in improving synovial blood flow and the bone erosion and there were significant differences among them neither the ultrasonic scores nor the pathological scores.The ultrasonic scores of synovial blood flow in TP group，BS group and TPN group（all P＜0.01） were lower than that of control group.The ultrasonic scores（all P＜0.05） and pathological scores（all P＜0.05） of bone erosion of other groups were also lower than that of control group.There were significant correlations between ultrasonic scores and pathological scores of synovial inflammation and bone erosion （r=0.832 and 0.859 respectively，both P＜0.001）.Conclusion High frequency ultrasound is a reliable imaging method to evaluate early arthritis and follow up treatment effect.Ultrasound-guided Intra-articular injection of TPN can relieve joint synovitis and delay the bone erosion，with slight side effect.