Abstract: To provide basis and reference for the utilization of walnut dietary fibers, walnut dietary fibers were extracted using chemical extraction methods and the physiochemical properties of five fibers with different particles sizes, including below 40 mesh, 40⁶0 mesh, 60⁸0 mesh, 80¹20 mesh, 120¹60 mesh and beyond 160 mesh, were also investigated.Results suggested that the yield of walnut dietary fibers, composing mainly of 76.34% of dietary fibers and 5.41% of protein, was 12.47%.Infrared spectroscopy scanning pictures indicated that walnut dietary fibers had remark absorbance at 3420 cm^-1, suggesting fiber structure had not been destructed.The significant differences of water-keeping capability, swelling capability and viscosity were observed during determining physiochemical properties of five dietary fibers with varying particle sizes.The best water-keeping capability, 7.76 g·g^-1, was observed in walnut dietary fibers with 120 ~ 160 mesh, and the best swelling capability and viscosity, 5.28 m L·g^-1, 21.25 m Pa·s, respectively, both were observed in dietary fibers with 80¹20 mesh.However, walnut dietary fibers size over 160 mesh had the best oil-keeping capability, with 1.92 g·g^-1. In addition, absorption capability of glucose was optimum at the particles 120 to 160 mesh, cation absorptin capability peaked at the particle range of 80 to 120 mesh.Overall, walnut dietary fibers with the particle size of 80¹60 mesh had the optimum physiochemical properties.