Pulmonary arterial hypertension (PAH) is a severe clinical and pathophysiologic syndrome with no effective treatment at present. Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), has been applied widely to the treatment of connective tissue diseases with the effect of immunosuppressant. Its anti-proliferation has been found recently. Thereby, we tried to examine the effects of MMF on rats with PAH which was induced by monocrotaline injection, so as to investigate the mechanisms of treatment on PAH by MMF. The results substantiated that MMF therapy can alleviate thickening of pulmonary arterial walls and inhibit abnormal vascular remodeling, and the MPA concentrations which demonstrated efficacy in this study are within clinical applicable range, suggesting huge potentiality of MMF in the treatment of human PAH.