Description: Background: The proceeding of blood pressure (BP) from normal level to the hypertension has been found to be associated with increased cardiovascular events and multiple vascular risk factors. However, whether the process is associated with increased carotid atherosclerotic plaque per se or not is still unclear. Methods: Nine hundred and forty-two participants aged from 46 to 75 were enrolled from community population in Southern China. Their metabolic risk factors, carotid intima-media thickness (cIMT) and atherosclerotic plaque formation were analyzed and stratified by different blood pressure levels according to JNC-7 or ESH/ESC-2007 classification. Results: From low BP level to higher BP level, multiple metabolic risk factors increased linearly. Prehypertension in JNC-7 classification (or normal BP and high normal BP in ESH/ESC-2007 classification) was correlated with thicker cIMT and more plaque formation than normotension (or optimal BP) (p 〈 0.001). After adjusting multiple metabolic factors, the differences were still significant (p 〈 0.05). Furthermore, prehypertensive participants had a trend to be thicker carotid IMT (OR and its 95% CI: 1.65, 0.97-2.82, p = 0.067) and significantly higher carotid plaque occurrence (OR and its 95% CI: 2.36, 1.43-3.88, p = 0.001) than normotensive ones. However, there was no significant difference of cIMT and plaque formation between normal BP and high normal BP (p 〉 0.05). Thus, we concluded that plaque formation in prehypertension was as significant as that in hypertension. Conclusion: Prehypertension is associated with significantly increased carotid atherosclerotic plaque and is a primary stratify risk factor for carotid atherosclerosis which could cause ischemic stroke in middle-aged and elderly population in Southern China.