Aim To investigate the effect of high saturated fatty acids and n-3 polyunsaturated fatty acid diet on arterial elasticity in spontaneously hypertensive rats （SHR）. Methods Thirty male SHR （8 weeks old）,adaptive feeding to 14 weeks old,were randomly divided into 3 groups by body mass: normal chow group（NFD）,high-fat diet group （HFD） and group of high-fat diet supplemented with fish oil group（HF+FOD） to 36 weeks old were intervened for 22 weeks. Thirty male Wistar-Kyoto rats（WKY） at the same age were divided into the same groups. After being intervened,the blood pressure,weight,serum free fatty acids （FFA）,biochemical index were measured. At the end of the feeding,artery pulse wave velocity （APWV）,using histochemical,pathological,change of centre arterial vascular wall and matrix metalloprotein-9 （MMP-9） were measured. Results Systolic blood pressure （SBP） in SHR+HFD group was higher than that in SHR+NFD group and SHR+HF+FOD group （160.5±5.5 mmHg vs 153.1±1.0 mmHg,155.1±6.7 mmHg,both P<0.01）. Compared with the SHR+NFD group,the membrane cross-sectional area （MCSA） increased （35500±8536 μm² vs 28348±3956 μm²,P<0.05）,aortic elastic properties in the SHR+HF group significantly decreased （21.1%±2.3% vs 30.7%±2.3%,P<0.05）. However,in SHR+HF+FOD group,such a marked increase of MCSA （16865±7235 μm² vs 35500±8536 μm²,P<0.05） and decrease of aortic elastic properties （34.5%±4.1% vs 21.1%±2.3%） were completely reversed （P<0.05）. The APWV was increased in the SHR+HF group compared with the SHR+NFD group. But it was significantly decreased in SHR+HF+FOD group compared with SHR+HF group. MMP-9 expression was higher in SHR+HFD group compared with that in SHR+NFD group and SHR+HF+FOD group. Conclusion The diet of high saturated fatty acid stimulates the thickness of aorta blood vessel in SHR and increases arterial stiffness,raises MMP-9 expression,dietary fish oil reduces MMP-9 expression,vascular wall thickness and increases aortic contents of elastin in SHR. This may contribute to decrease blood pressure.