Abstract： Objective To explore the value of high-resolution MRI(HR-MRI) on clinical application in the differential diagnosis between Moyamoya disease(MMD) and atherosclerosis-related Moyamoya syndrome (A-MMS). Methods Seventeen cases of patients with MMD and 18 cases of patients with A-MMS in our hospital from January 2014 to September 2015 were prospectively enrolled in the study. Record the clinical data and the proximal middle cerebral artery (M1 portion) performance on HR-MRI, the max-vessel area, the min-vessel area, the max-lumen area, the min-lumen area, the wall max-thickness, the styles of M1 portion thickening (eccentric or concentric), whether the wall was enhanced or not, and analysis the recorded data statistically, t test and χ2 test were used for the statistical analysis. Results The wall max-thickness of MMD group was (0.94 ± 0.17) mm, which was smaller than that in A-MMS group (1.23 ± 0.42) mm, there was statistic significance (t=-2.977, P=0.006). The cases of M1 portion non-enhancement was 15, slight enhancement 2, strong enhancement 0 in MMD group, and non-enhancement 5, slight enhancement 5, strong enhancement 8 in the A-MMS group, the difference was significant statistically (χ2=9.794, P=0.001). The cases of M1 portion concentric thickening was 16, 9 cases in the A-MMS group, there was statistic difference between them (χ2=6.317, P=0.012). Wall concentric thickening diagnose the MMD with a sensitivity of 94.1% (16/17), specificity of 50.0% (9/18), accuracy of 71.4%(25/35). Wall strong enhancement appear in the A-MMS with a sensitivity of 44.4%(8/18), specificity of 100%(17/17), accuracy of 71.4%(25/35).With a cut-off the maximum wall thickness of 1.2 mm could be used to noninvasively differential diagnose the MMD and A-MMS with a sensitivity of 55.6%(10/18), specificity of 88.2%(15/17), accuracy of 71.4%(25/35). Conclusion HR-MRI is a good tool for the differential diagnosis between MMD and A-MMS.