This study evaluated the effect of grinding methods (regular laboratory milling, ultra centrifugal rotor milling, and ball milling) on structural, physicochemical, and functional properties of insoluble dietary fiber (IDF) fraction from orange peel. The results demonstrated that both ultra centrifugal milling and ball milling could effectively decrease average particle size of IDF fraction (81.40 μm and 19.63 μm, resp.). The matrix structure of IDF fraction was destroyed but FTIR structure had no major change after grinding. As particle size decreased, the bulk density and lightness of IDF fraction increased and a redistribution of fiber components from insoluble to soluble fractions was observed. Furthermore, ball milled IDF fraction exhibited significantly higher capacity to retard glucose diffusion and inhibit α-amylase activity (35.09%). This work would give useful insight into effect of grinding methods on properties and functions of orange peel IDF in food industry.