【Objective】To explore the efficacy of T2 * mapping for evaluating inflammatory activity in the patients with Crohn disease（CD）.【Methods】A total of 98 CD patients underwent MR enterographywith T2 * WI. T2* values were measured by put? ting regions of interest on the thickening bowel wall on T2 * mapping. The activity of bowel segment was scored by magnetic resonance index of activity（MaRIA），to analyze the relationship between T2 * values with CD activity. 【Results】A total of 160 bowel segments were evaluated and includedinactive（MaRIA < 7，n = 26），mild（7 ≤ MaRIA < 11，n = 23），and moderately-severe（MaRIA ≥ 11， n = 111）active lesions. The differences in T2 * values amongthese three groups were significant（all P < 0.05）. T2 * values of 160 bowel segments correlatedclosely withMaRIA（r = 0.743，P < 0.05）. High accuracy of T2 * values was shown for differentiating inac? tive from active CD（AUC=0.877）anddifferentiating inactive-mild from moderate-severe CD（AUC = 0.848）. The threshold T2 * value of 20 ms allowed differentiation of mild from moderate-severe CD with74.5% sensitivity and 84% specificity. 【Conclusions】T2 * values， as thequantitative indexof T2 * mapping，correlate well with CD activity and showsatisfiedefficacy for diagnosing inflammatoryactivity.