Abstract: OBJECTIVE To investigate the in vivo pharmacokinetic properties and bioavailability of norisoboldine and its major metabolite in rats after intravenous and oral administration. METHODS A UPLC-MS method was used to determine the plasma concentrations of norisoboldine and norisoboldine-9-O-α-glucuronide in rats plasma. The pharmacokinetic parameters were calculated with PK solution software. RESULTS The absolute bioavailabilities for norisoboldine and norisoboldine-9-O-α-glucuronide were 2.77% and 88.6%, respectively. After intravenous injection of norisoboldine, the main pharmacokinetic parameters of norisoboldine and norisoboldine-9-O-α-glucuronide were as follows: t_1/2 (42.16±36.56) and (275.26±176.89) min, AUC_0-t(55.25±22.97) and (584.57±216.18)mg·min·mL^-1, k_e (0.024 9±0.012 9) and (0.003 7±0.002 4)min^-1, respectively. Their major pharmacokinetic parameters after oral administration were as follows: C_max (0.14±0.03) and (13.80±1.46)mg·mL^-1, T_max (3.33±13.29) and (45.00±9.49)min, t_1/2 (30.20±11.04) and (313.79±181.20)min, AUC_0-t (9.17±2.44) and (3 108.69±299.45) mg·min·mL^-1, k_e (0.025 2±0.007 6) and (0.002 7±0.001 0)min^-1, respectively. There were significant differences between oral and intravenous administration in t_1/2, AUC_0-t, T_max, C_max, k_e and MRT (P<0.05). CONCLUSION The absolute bioavailability for norisoboldine was poor in rats. Norisoboldine could be quickly biotransformed into norisoboldine-9-O-α-glucuronide, a major metabolite of parent drug in vivo, and the plasma concentration of norisoboldine-9-O-α-glucuronide was considerably higher than that of the parent drug.