The primary objective was to develope a UPLC method for determine the concentration of buspirone hydroxychloride in plasma and to evaluate the effects of Aconiti Laterlis Radix and Aconiti Laterlis Radix compatibility of Glycyrrhizae Radix on CYP3A4 in vivo. ACQUITY UPLC BEH C18 column (2.1 mm x 10 mm, 1.7 microm) was used for the gradient elution with a 2.0 mmol x L(-1) ammonium acetate (pH 7.4, A)-acetonitrile (B) solution, 0-2.2 min, 10% - 60% B, 2.2-2.5 min, 60% B, 2.5-3.0 min, 60%-75% B, 3.0-3.5 min, 75% B, 3.5-4.0 min, 75%-10% B, at the flow rate of 0.3 mL x min(-1) at room temperature. The UV wavelenght was detected at 243 nm. The linear calibration curve ranged between 0.078 125-20.0 microg (r = 0.9975). The average recovery (n = 6) of buspirone hydroxychloride was 85.62% (RSD 6.8%). The results showed that this method has good specificity and repeatability, and which can be used for the determination of buspirone hydrochlorid in serum. In animial studies, single dose Aconiti Laterlis Radix extract treatment (0.5 g x kg(-1)) decreased buspirone hydroxychloride AUC(0-2 h) (52.8%, P = 0.020), increased CL/F (122%, P = 0.045). Compared to the saline treatment group, Aconiti Laterlis Radix compatibility of Glycyrrhizae Radix extract treatment has no effect on CYP3A4 in rat. The results indicated that Aconiti Laterlis Radix extract induced CYP3A4 while Aconiti Laterlis Radix compatibility of Glycyrrhizae Radix extract had no effect on CYP3A4 in vivo. Aconiti Laterlis Radix had been detoxified when be used as compatibility of Glycyrrhizae Radix.