Objective To investigate the pathogenesis of portal hypertensive gastropathy(PHG). Methods Two rat models with portal hypertension(PHT) and a sham operation group were established to detect the pathological changes in histology and ultrastructure of the gastric mucosa as well as quantitative changes in histological morphology by graphic analysis computer system. Results Prominent edema, scattered red dots/ecchymosis were found in gastric mucosa in rats with PHT. Light and scan electron microscopy showed swelling or exfoliating of the epithelium cell, reduction of gastric gland number, thin of gastric mucosa, while infiltration of inflammatory cells, epithelium metaplasia were not found. The most characteristic findings were the changes of the mucosal capillaries and venules in both mucosal basal lamina and submucosa layer light microscopically, as well as the transmutation, stenosis and loose intercellular joining of the capillaries on electron microscopy. Ultrastructure observation revealed numerous pinocytes in epithelial cells as well as proliferation and hyperplasia of smooth muscle, collagenous fiber and extracellular matrix in venules. Quantitative analysis showed that the ratios of the cross sectional area and the vascular wall area between the gastric wall area(CSA/GWA & VWA/GWA) was higher in liver cirrhosis(LC) and portal vein stenosis(PVS) groups than that in sham operation(SO) group. There was a positive correlation between portal vein pressure and the ratio of the length of damaged mucosa and the length of mucosa(LDM/LM that was higher in LC group than in PVS group). Conclusions In rats with cirrhotic portal hypertension, distinct gastric microvascular morphological changes are the major etiological factor of PHG as a part of pathological changes in portal hypertension.