Micro Metal Injection Molding utilizing 316 steel nanopowder with 100 nm in mean size was investigated to fabricate micro part. The nanopowder was used since its advantages to produce better surface roughness and detail structure in the micro part fabrication. During nanopowder preparation, thin oxide must be formed intentionally to avoid powder burnt before it's exposed to the air during mixing with the wax binder system. Unfortunately, this oxide still exist after sintering and decrease the mechanical properties (ductility and densification) by the formation of secondary phase which detected as chrome oxide. In this paper, deep elaboration for oxide characteristics and the ways to reduce it by vary the sintering parameters and in Hydrogen atmosphere were described briefly. Here, we infer by reducing the heating rate, increasing the sintering temperature and utilizing the Hydrogen atmosphere can be effectively optimize the utilizing of nanopowder for micro part fabrication.