Objective:To investigate and compare the diagnostic value of dynamic contrast-enhanced MRI(DCE-MRI)and musculoskeletal ultrasound(MSUS)for the activity of rheumatoid arthritis(RA).Methods:The clinical data of 97 patients with RA who received DCE-MRI and MSUS in the hospital were retrospectively analyzed.The detection rates of typical pathological features of RA patients by DCE-MRI and MSUS at admission were compared.The patients were divided into an active group(DAS28 ≥2.6 points,n=56)and an inactive group(DAS28＜2.6 points,n=41)according to the disease activity[rheumatoid arthritis disease activity sco-ring system(DAS28)score].The quantitative parameters of DCE-MRI[early enhancement rate(EER),maximum enhancement rate(MER),time to peak(TTP)]and MSUS[synovial thickness,blood flow signal score,synovial artery resistance index(RI)]of pa-tients with different disease activities were compared at admission.The diagnostic efficiency of quantitative parameters of these two ima-ging techniques for the disease activity of RA patients was analyzed by receiver operating characteristic curve(ROC).Results:There was no statistical significance in the detection rate of synovial hyperplasia in RA patients between the two imaging techniques(P＞0.05).The detection rate of bone erosion in RA patients by DCE-MRI was higher than that by MSUS while the detection rate of joint ef-fusion was lower than that by MSUS(P＜0.05).At admission,the EER,MER,synovial thickness and blood flow signal score in active group were higher while the TTP and synovial artery RI were lower than those in inactive group(P＜0.05).ROC analysis showed that the areas under the ROC curves(AUCs)for EER,MER,TTP,synovial thickness,blood flow signal score and synovial artery RI were 0.788,0.846,0.806,0.865,0.626 and 0.819,the sensitivities were 75.61％,92.68％,70.73％,78.05％,87.80％and 75.61％,and the specificities were 71.43％,64.29％,76.79％,78.57％,32.14％and 82.14％,respectively(P＜0.05).Conclusion:Both DCE-MRI and MSUS have good diagnostic value on RA activity,but DCE-MRI has a higher detection rate of bone erosion in RA pa-tients,while MSUS has a higher detection rate of joint effusion.