Objective:To evaluate the relationship of the shape,location of superficial calcification with surface ulcer,intraplaque hemorrhage in the atherosclerotic carotid plaque (ACP).Methods:Fifty-one patients received pre- and post-contrast high-resolution 3T MRI for ACP and a total 183 layers with superficial calcification were enrolled in our study.The shape of the superficial calcification was categorized as irregular type(dotted/arcuated) and patch type; the location of the calcification was categorized as marginal type and central type.Intraplaque hemorrhage and surface ulcer at the same or adjacent slice to the superficial calcification were identified.Chi-Square test was used to analyze the relationship of the shape,location of superficial calcification with surface ulcer and intraplaque hemorrhage.Results::We found that 122(66.7%) of the 183 slices had intraplaque hemorrhage and 86(47%)slices had surface ulcer.We also found that 158 slices had irregular type(dotted/arcuated)calcification and 142 slices had marginal calcification.Irregular superficial calcification was found more frequently with intraplaque hemorrhage than patch type (72.8% vs 28%,P<0.01).Marginal type had higher possibility of intraplaque hemorrhage than central type did (71.1% vs 51.2%，P<0.05).However,the incidence of surface ulcer was not significantly different between different types and locations of superficial calcification.Conclusion:It can be concluded that superficial calcification is an important factor for instability of atherosclerotic carotid plaque.The shape and location of superficial calcification are important factors of intraplaque hemorrhage.