The cluster of hypertension, diabetes mellitus, dyslipidemia and body obesity, collectively referred to as the metabolic syndrome, is a common cause of atherosclerotic and cardiovascular diseases, and also one of the most serious threats to public health. Metabolic syndrome is closely related to micro-inflammation, which receives great attention in recent years. Besides the hemodynamic regulatory role, renin-angiotensin system (RAS) also plays an important role in micro-inflammation. Blockade of RAS could protect against the development of metabolic syndrome. It has been confirmed that RAS exerts its effects mainly through angiotensin converting enzyme(ACE)-angiotensinⅡ(AngⅡ)-angiotensin 1 receptor(AT1R) axis and ACE2-Ang(1-7)-Mas axis, and the two approaches have opposite biological activities. Angiotensin(Ang)Ⅱ could initiate inflammation through a variety of mechanisms by its receptors, but the Ang1-7, as the antagonists to AngⅡ, restrains the inflammation. In this paper, we reviewed the mechanism through which RAS is involved in micro-inflammation.