Abstract: Nanotechnology has become one of the most important and interesting fields of physics, chemistry, biology and engineering in recent years. One of the developing nanotechnology developments is nanoparticles. The polymers used to form nanoparticles can be synthetic and natural polymers. One water-soluble polymer that can be used in the manufacture of nanoparticles for the purpose of treatment is chitosan. The availability of crab waste has a huge potential to serve as a raw material for making chitosan. Chitosan is a modification of many chitin compounds present in the outer skin of crustaceae class animals such as shrimp and crabs. This study, aims to synthesize chitosan from crab shells in the form of nanoparticles. The chitin isolation step includes demineralization process with HCl 1 N and deproteination with 3.5% NaOH. Chitin transformation into chitosan through the deacetylation stage with 50% NaOH. The making of nanoparticles is done by addition of TPP solution. The result showed that chitin transformation became chitosan 66.64% with deacetylation degree 76.69% and chitosan particle size 386.3 nm.