Abstract: Objective To investigate the method and key points of monocrotaline injection in establishing pulmonary hypertension model of rats. Methods Thirty Sprague dawley (SD) male rats of SPF grade were randomly divided into two groups: experiment group (n=15) and control group (n=15). The experimental rats received subcutaneous injection of monocrotaline accounting for 50 mg/kg, and rats in control group received subcutaneous injection of 0.9% sodium chloride accounting for 1 ml. Three weeks later, the rats underwent right heart catheterization, pathology and immunohistochemistry. Results Rats in experimental group showed progressive right heart failure with 2 rats died. The mean pulmonary artery pressure and right ventricular systolic pressure in experimental rats were significantly higher than control group (40.05±1.78) mmHg vs (18.63±1.80) mmHg (1 mmHg=0.133 kPa), (62.99±2.03) mmHg vs (28.04±2.26) mmHg, P< 0.05. HE staining showed rats in the experimental group with pulmonary vascular membrane hyperplasia and stenosis, and WT%, WA%, RV/(LV + IVS) in rats of experimental group were significantly higher than control group (0.292±0.064) vs (0.106±0.026), (0.0495±0.092) vs (0.200±0.045), (0.473±0.041) vs (0.295±0.035), P< 0.05. IA value of pulmonary vascular PCNA immunohistochemistry in experimental group was significantly higher than control group (39.5±8.7) vs (18.5±5.3), P< 0.05. Conclusion Monocrotaline injection in establishing rat model of pulmonary hypertension is a simple, effective and reliable method, and the modeling success rate can be improved with a few key points.