【Abstract】 Objective To evaluate the accuracy in estimating pulmonary arterial pressure (PAP) with four ultrasonic Doppler modalities in rats treated with monocrotaline (MCT). Methods The total of 41 male rats at the age of 8 weeks were divided into control group( Con group: n=11) and monocrotaline group（MCT group: n=30）. Four weeks after treatment, The pulmonary arterial acceleration time (PAAT), pulmonary arterial ejection time (PET) and tricuspid regurgitation peak flow velocity (TR peak) were measured with Continuous-Wave Doppler. The invasive PAP was applied as gold standard to assess the correlation with such following ultrasonic parameters as PAAT, PAAT/PET, PAAT/HR (heart rate) and TR peak. Results The PAAT, PAAT/PET, PAAT/HR and TR peak were closely negatively-correlated with the invasive mean pulmonary arterial pressure (PAP)（R＝0.49, 0.469, 0.267, 0.173; p＜0.05）. TR peak had the lowest relationship with the mean pulmonary artery pressure. ROC curve showed that PAAT/PET had the highest diagnostic value and its cut off value of 0.381 had 0.818 and 0.90 in sensitivity and specificity respectively on estimating pulmonary arterial hypertension . Conclusion The ratio of PAAT to PET was more reliable to assess pulmonary artery pressure in rats compared with TR peak.