[Objective] To establish a rat model of early sacroiliac arthritis (SIS) induced by bovine proteoglycan in ankylosing spondylitis (AS).To evaluate the value of early imaging diagnosis of AS, DCE-MRI were used to measure the parameters of magnetic resonance imaging in the lesion area. [Materials and methods] Bovine proteoglycan combined with CFA/IFA was used to induce SIS in 20 male rats as experimental group, and 20 healthy rats of the same kind were selected as control group. DCE-MR quantitative parameters Ktrans, Kep and Ve were measured at 7, 12, 17 and 22 weeks after induction respectively. The pathological characteristics of sacroiliac region of as rat model were studied by extracting the pathological features of SIJ after cervical execution. Pathological examination of SIJ after execution. Independent sample t-test and ROC curve were used for statistical analysis. [Result] At the 17th week after induction, inflammatory cell infiltration appeared in SIJ of experimental group. The values of Ktrans and Kep in experimental group were higher than those in control group , the difference was statistically significant (P = 0.000, 0.000, P < 0.05); The area under ROC curve of Ktrans and Kep was (0.891, 0.843), the critical value (sensitivity, specificity) was Ktrans = 0.295/min (100%, 65%), Kep = 0.591/min (90%, 60%). At the 22nd week, infiltration and destruction of cartilage were found in sacroiliac joint area of experimental group, the values of Ktrans, Kep and Ve in the experimental group were higher than those in the control group in the same week, the difference was statistically significant (P values were about 0.000, 0.000, 0.000, P < 0.05); The area under the ROC curve of Ktrans is the highest (0.995). The critical value (sensitivity, specificity) is Ktrans = 0.345/min (95%, 100%). [Conclusion] The quantitative data of DCE-MRI sequence can reflect the changes of local microenvironment in the early stage of inflammation and provide imaging evidence for the clinical diagnosis of As.