Abstract: In order to find out the quantitative relationship between physicochemical properties of drugs and their nasal absorption, diltiazem hydrochloride and paracetamol were selected as model drugs and their octanolwater partition coefficient was determined. In situ nasal recirculation method at different pH values was used to estimate the rate constant of nasal drug absorption in rats. Results showed that quantitative relationship existed between partition coefficient and nasal absorption constant, with correlation coefficient being 0.9761(n=9). Besides methods of partition coefficient determination, the in situ nasal recirculation manipulation was also improved.