The extraction technology of dietary fiber from Jiangyong pomelo peel by microwave assisted alkali method was established and the physicochemical properties and antioxidant activity of dietary fiber were analyzed. The results showed that, ensuring the extraction rate of soluble dietary fiber preferentially, the optimum extraction process of dietary fiber were solid-liquid ratio of 110 (g/mL), NaOH concentration of 8%, microwave time 40 s and microwave power 350 W. With the contrl of the optimal conditions, the maximum extraction yield rate of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) was 40.8% and 45.1%, respectively. Moreove, the dietary fiber showed fine water holding capacity (SDF: 5.3 g/g; IDF: 3.5 g/g), swelling capacity (SDF: 5.1 mL/g; IDF: 2.4 mL/g) and oil holding capacity (SDF: 4.6 g/g; IDF: 2.1 g/g). In addition, the a good antioxidant activity was also found in the dietary fiber, which could scavenge DPPH radicals and inhibit the oxidation of vegetable oil. The free radical scavenging rate of SDF was significantly higher than that of IDF and BHT (t-test, P＜0.05) when these concentration reached 2 mg/mL.Finally, the inhibitory effect on POV of vegetable oil under the same mass fraction was SDF＞IDF＞BHT.