Abstract: OBJECTIVE To observe the effects of nisoldipine(NIS) on the contractile response of isolated rat pulmonary artery induced by KCl and phenylephrine(PHE) and explore the effect of nisoldipine on monocrotaline-induced pulmonary hypertention(PH) in rats. METHODS ①Isolated artery experiment was used to observe the antagonistic effects of NIS on the contraction of isolated rats’ pulmonary arteris induced by KCl and PHE in the calciferous and calcium-free K-H solution. ②Forty Wistar rats were randomly divided into 4 groups: normal group, modle group , NIS group and nifedipine(NIF) group. Rats except those in normal group were injected with a single dose of moncrotaline(50 mg·kg^-1) to induce PH. Rats in each group were administrated with corresponding drugs for 21 d. The mPAP, mRVP, maxPAP and maxRVP were measured by right cardiac catheterization, and RVHI and LI were calculated. RESULTS ①In the calciferous K-H solution, the contractile response of rats’ isolated pulmonary arteris induced by KCl(20, 40, 60 mmol·L^-1) and PHE(1×10^-7, 5×10^-7, 1×10^-6 mol·L^-1) were inhibited by NIS. The IC₅₀ was 0.87×10^-8, 1.41×10^-8, 8.32×10^-8 mol·L^-1 and 0.56×10^-7，4.27×10^-7，1.28×10^-6 mol·L^-1, respectively. In the calcium-free K-H solution, NIS had no effect. ②The mPVP, mRVP, maxPAP, maxRVP, RVHI and LI in model group were higher than those of the normal group(P<0.01), and the above indexes in NIS group and NIF group were lower than those of the model group(P<0.05). CONCLUSION NIS can inhibit the contractile response of rats’ isolated pulmonary artery, and it has therapeutical effect on monocrotaine-induced pulmonary hypertension in rats.