Abstract: The effect of ligustrazine hydrochloride (LTH) on depressing pulmonary arteryhypertension has been proved in recent studies.In an attempt to prepare a lung targeting dosage form,ligustrazine hydrochloride gelatin microspheres (LTH-GMS)were prepared by the method of emulsionprocess,using 2:1 as the weight ratio of LTH to gelatin. The preparation technique was optimizedand the apl1earance,particle size and size distribution,LTH content,in vitro release,stability,and in vivo distribution of LTH-GMS were studied.The results showed that the mean diameter of LTH-GMSmeasured by Coulter counter was 12.65μm,87.5% of the microspheres ranging from 5 to 24.9μm.The average content of LTH in LTHGMS was 16.49%±0.49%(n=3)with an average extent ofentrapment of abOut 89%and the LTH-GMS were stable for three months when stored in refrigeratoror at rcom temperature. The release profile in vitro(pH 7.8～8.0 phosphate buffer)can be describedby first-order kinetic equation. The release t_1/2 of LTH when given LTH-GMS was about 6 times asmuch as that of original LTH, The relative distribution percentage of LTH-GMS in lung whendetermined 20 min after iv administration to mice was significantly higher than those of LTH-GMS inother tissues and blood,and was about 6 times as much as that of the LTH solution control group inlung under the same conditions.