Based on low molecular weight water- soluble chitosan (LMWSC), LMWSC was chemically modified with deoxycholic acid (DA) which is one of the bile acid as a hydrophobic group. LMWSC- Deoxychohc acid nanoparticles(WSCDA) using DA conjugated LMWSC were characterized using dynamic hght scattering(DLS) and transmittance electron microscope (TEM) . The particle sizeof WSCDA ranged from 250 to 350 nm and increased with the number of DA substitution. WSCDA has the superior potential for the application biomedical field.