Aim To observe whether the level of endothelin (ET), atrial natriuretic peptide (ANP) and calcitonin gene related peptide (CGRP) in the plasma of rats with pulmonary hypertension (PH) can be influenced by exogenous nitric oxide. Methods A monocrotaline (MCT) PH model was founded in rat. Exogenous NO were inhaled during the forming and developing of PH. The changes of ET, ANP and CGRP and systolic pressure of right ventricle (RVSP), mean cervical arterial pressure were measured. Results It demonstrated that the RVSP of MCT rats had been elevated since the first week: from 1.71±0.35 kPa to 2.35±0.44 kPa, and (PH) was formed at the time of the third week: 4.56±0.65 kPa, the plasma concentration of ET and ANP in MCT rats were increased along with pulmonary arterial pressure, ET: from 130±4 ng/L, elevated to 187±37 ng/L; ANP: from 172±28 ng/L elevated to 207±27 ng/L at the first week, but CGRP were lowered: from 232±57 ng/L reduced to 187±23 ng/L at the first week. After exogenous NO were inhaled intervally at long term, ET and ANP have the tendency to reduce: ET reduced from 636±148 ng/L to 534±44 ng/L; ANP reduced from 1 111±248 ng/L to 772±145 ng/L. But CGRP increased from 45±11 ng/L to 80±16 ng/L at the fifth week, RVSP lowered from 2.35±0.44 kPa to 2.02±0.29 kPa at the first week. In comparison with control group, there is a significant difference (p<0.05). Conclusions There is a positive significant correlation between the forming and developing of PH and plasma concentration of ET and ANP, but negative significant correlation with CGRP. The methods of interval and long term time of inhaled exogenous NO could not only attenuate the forming of PH and partly prohibit the process and progress of PH, but also had an effect on the formed PH.