Objective To establish the rat model of collagen-induced arthritis and study the diagnostic value of MRI for early RA by comparing to pathological changes. Methods Thirty Wistar rats were randomly divided into normal groups and experimental groups.Fifteen rats of the experimental groups were immunized with type Ⅱ collagen and Freund's Adjuvant Incomplete. At the scheduled days, the selected rats of both experimental and normal groups underwent X-ray, 1.5T MR scan plus enhancement and histological analysis. Results Arthritis Index increased on the 14th day after immunization and reached the peak on the 28th day in the experimental group, the positivity of Anti-CⅡ antibody was significantly different from the normal group.The experiemental model was established in 93.33% of all rats. The enhanced MRI showed that 12 (12/15) rats presented with abnormal signs . The sensitivity of MRI was 85.71% and the specificity was 100%. There was no significant correlation could be found between MRI and histological changes X-ray revealed soft tissue swollen in 4 (4/15) rats, which showed that MRI had higher sensitivity in detecting abnormal signs of arthritis than X-ray. Conclusion MRI may be used in the early diagnosis of early RA.