Abstract: Equilibrium solubility of NCP4 at different pH levels was determined by HPLC and shaking flash method was used to detect its partition coefficients in the n-octanol-water,hydrochloric acid,buffer solution systems.With the condition of 37 °C,the equilibrium solubility of NCP4 in water,hydrochloric acid (pH 1.0) andphosphate buffer solution（pH 2.0,3.0,4.0,5.0,6.0,6.8,7.0,7.4,8.0）were 3.68,24.81,6.25,4.91,6.53,5.98,4.20,4.46,6.39,5.97,17.41 μg/L.In the addition,the lgP（O/W） of NCP4 also in the above condition were 7.31,7.37,not detected (ND),ND,7.40,ND,ND,7.57,6.73,7.43,7.44,respectively.Determination of equilibrium solubility and partition coefficients of NCP4 can provide the basis for its dosage form.The detected values of lgP（O/W） of NC/P4 were more than 5,indicating that NCP4 was not easy to absorb on mucosa.