Objective: To prepare oligoprocyanidins from Seabuckthorn seed meal by ultra-high pressure pretreatment and ultrasonic extraction， and analyze its structure and antioxidant properties. Box-Behnken adopted to optimize the preparation process of oligoprocyanidins from seabuckthorn seed meal. Infrared Spectroscopy(IR) and Ultra performance liquid chromatography-mass (UPLC-ES-MS) spectrometry were used to analyzed the structure and the antioxidant activity was determined by DPPH， ABTS and FRAP. Result: The optimal process parameters were 1∶15 (g/mL) material-to-liquid ratio， ultrasonic time 28 min， ultrasonic temperature 45 ℃， solvent pH 2.85， the sea buckthorn seed meal proanthocyanidin yield was 6.556%， and the average degree of polymerization was 3.35， which mainly composed of dimer， trimer proanthocyanidins and some flavonoids. The dimers include three B-type dimers and one A-type dimer. The Sea buckthorn meal oligoprocyanidins showed good antioxidant activity， with DPPH， ABTS and FRAP values of 2.205， 1.307 and 0.8143 mmol Trolox/g DW， respectively. Conclusion: oligoprocyanidins from Seabuckthorn seed meal have strong antioxidant activity， and are structurally distinct from proanthocyanidins from grape seed meal.