A new chitosan derivate (CMC-g-RA) was prepared by grafting ricinoleic acid anhydride (RA) on carboxymethy chitosan (CMC) molecules. The reaction factors such as molecular weight, mole ratio of anhydride to amino, temperature and solvent were examined. Nanoparticles were obtained by blending botanical insecticide capsaicin (Cap) and CMC-g-RA. Surface shape, particle size, polydispersity index, surface charge, LE and stability of Cap/CMC-g-RA nanoparticles were characterized. The results showed that lower molecular weight was of advantage to higher degree of RA substitution. CMC-g-RA and Cap formed drug delivery nanoparticles with spherical shape and negative surface charge in water. The increased concentration of drug or carrier resulted in higher zeta potential and narrower polydispersity index (PDI) of Cap/CMC-g-RA. The loading efficiency (LE) of nanoparticles was up to 0.86, which provided efficiently protection for Cap, extended drug releasing period and dosage.