Objective To study the relationship between portal hypertension(PHT) and heme oxygenase-1(HO-1)mRNA expression in rats.Method An animal model of PHT induced by partial portal vein constriction was established to detect the expression of HO-1mRNA in the liver,spleen, and splenic vein of rats by situ hybridization method. Result HO-1mRNA was not detected in the liver, spleen, and splenic vein in the control group. In PHT rats, HO-1mRNA was not detected in the liver;but in the spleen,the expression of HO-1mRNA was 83.3%;in the splenic vein,the expression was 55.6%. Conclusions The PHT rat is in stress condition.The expression of HO-1mRNA in the spleen and splenic vein of PHT ratsare increased and the metabolic product of HO-1 may exacerbate the PHT.