This paper presents a method by using a compensative structure assisted to fabricate deep lateral single-crystal-silicon (SCS) blaze micro-grating at Inductively-Coupled-Plasma Reactive Ion Etch (ICP-RIE). Due to the high resolution of blaze micro-grating, it's hard to maintain the teeth structure of blaze micro-grating under deep silicon etch in ICP-RIE process. Here, the independent rectangular structure and symmetrical structure to micro-grating is designed to obstruct the non-vertical plasma ion to etch the sidewall of micro-grating structure and to get better the profile control at deep micro-grating structure. The lateral silicon blaze micro-grating with 100 μm thickness by compensative structure assisted etch process have been successfully demonstrated this method.