Objective To explore the correlation between 18F-NaF micro-PET/CT,μCT score and histopathology of collagen-induced arthritis (CIA) rats.Methods Seventy healthy female SD rats were randomized into CIA group (n＝50) and control group (n ＝ 20).Micro-PET/CT imaging was performed 10 days after successful modeling.Minimum standardized uptake value (SUVmin),maximum standardized uptake value (SUVmax),mean standardized uptake value (SUVmean) and μCT score were measured,and the severity of rheumatoid arthritis was assessed with histopathology.The correlations between SUVmin,SUVmax,SUV μCT score and histopathology of CIA were analyzed.Results SUVmin,SUVmax,SUVmean,μCT score of CIA all showed positive correlations with histopathology (r＝ 0.920,0.943,0.923,0.768,all P＜0.001).Conclusion 18F-NaF micro-PET/CT is a quantitative imaging method for evaluating bone erosion and bone malformation in rat rheumatoid arthritis models of CIA,which is superior to μCT examination.