Abstract: O-hydroxypropyl-N-octyl chitosan(C₈-HPCS) was prepared by reacting 1-octyl bromide with Ohydroxypropyl chitosan(HPCS) under microwave heating. HPCS was prepared with chitosan and propylene oxide in presence of phase transfer catalyst tetrabutylammonium bromide. The intermediate HPCS and the objective product C₈-HPCS were characterized by FTIR and ¹H NMR spectroscopy. The results show that C8-HPCS has an excellent integrated performance when the reaction time is 50 min,the temperature is 65℃,the dosage of bromooctane is 8 mL and the dosage of tetrabutylammonium bromide is 0.07 g. The foamability, foaming property and emulsibility are 3.9 cm,88.9% and 78.1%,respectively. The critical micelle concentration of C₈-HPCS is 0.015 g/L with the surface tension of 58.5 mN/m and the hydrophile lipophile balance number is 13.44. The thermal stability analysis shows that the C₈-HPCS is stable up to 270℃ and the XRD analysis indicates that the quaternized chitosan is completely amorphous.