Objective: To investigate the relationship between age or period of hypertension and morphological remodeling of renal arterioles. Methods: Under dilated conditions, the morphometry of the renal arterioles were studied microscopically on kidney slices combining computer-assistant image analysis in 16, 26, 40 and 55 weeks of SHR. Results: Compared with age-matched Wistar-Kyoto, the wall thickness and ratio of wall thickness to inner diameter were much increased in the renal arterioles, while the wall area in the arterioles of 50 to 200 μm outer diameter increased. The inner diameter decreased in the arterioles of 20 to 50 μm outer diameter in 40 and 55 weeks of SHR. Hypertension and age were both related to the morphological remodeling of renal arterioles in SHR. Conclusion: Hypertension is the main reason of the remodeling of the renal arterioles in SHR from 16 to 55 weeks. The remodeling of the renal arterioles less than 50 μm outer diameter is due to the rearrangement of medial smooth muscle cells (SMC), but the remodeling of the renal arterioles more than 50 μm outer diameter is due to proliferation of the medial SMC.