This study aimed to explore the assessment value of HRMRI and PWI in patients of TIA with unilateral MCA atherosclerotic stenosis. 43 patients with MCA territory symptoms underwent preliminary DWI and MRA to exclude acute cerebral infarction and ascertain unilateral stenosis of MCA M1 segment. Thereafter, all the patients underwent HRMRI and PWI. HRMRI gets 155 positive slices，type Ⅲ of plaque 49 (31.6%), IV~Ⅴa 41 (26.5%),Ⅴb 4 (2.5%), Ⅵ 13 (8.4%),Ⅴc 48 (31.0%). The soft plaques(type Ⅳ~Ⅴa and VI) adds up to 54 (34.8%), hard plaques (type III,Ⅴb andⅤc) 101 (65.2%). HRMRI diagnosed four cases of mild stenosis, 11 moderate, 22 severe and 6 occlusion. 42 patients has hemisphere perfusion difference between the affected and normal MCA perfusion districts, with lower rCBF , longer rMTT and TTP (P <0.05) in the affected side. HRMRI can assess AHA sub-type and stability of atherosclerotic plaque, and stenosis rate of MCA, MTT, TTP can be found changes in early ischemic events, which are sensitive parameters to diagnose TIA.