Rayleigh light scatterings of 1,4-dioxane(D)-water(W) binary mixtures at 546 nm have been measured at 25 °C by using a conventional fluorometer. Mean-square concentration fluctuation ( N<( Δx) 2>) and Kirkwood-Buff parameters (KB integrals) of the mixtures at 1,4-dioxane mole fraction range of 0.0 ≤ x dio ≤ 1.0 have been estimated from the scattering results. The N<( Δx) 2> of the mixtures increase only slightly with the increase of 1,4-dioxane at x dio ≤ 0.13; at x dio > 0.13, however, the N<( Δx) 2> increase abruptly with increasing x dio and show a maximum of N<( Δx) 2> = 3.4 at x dio = ∼0.7. For mixtures at x dio > 0.7 the N<( Δx) 2> decrease monotonously with increasing x dio. KB integrals of the 1,4-dioxane-water mixtures ϱ D G DD, ϱ W G WW, and ϱ D G DW show maxima or minima at x dio = 0.3 or 0.7, suggesting the changes in local structure of the mixed solvent at these compositions. From the analyses of the N<( Δx) 2> and KB integrals of the 1,4-dioxane-water mixtures, it is concluded that local structure of the mixed solvent changes at three specific compositions, x dio = 0.13, 0.3, and 0.7, respectively. The mixtures at x dio ≤ 0.13 are composed of mainly water associates and water-dioxane complexes DW l ( l = 6–8). Small clusters of water-dioxane molecules (D 1–3W 7–21) through hydrogen bonding are formed in mixtures at 0.13 ≤ x dio ≤ 0.3. The hydrogen bonded molecular clusters coexist with 1,4-dioxane aggregates D n ( n = ∼10) in the mixtures at x dio > 0.3. The local structure of the mixtures at x dio > 0.3 evolves gradually to the inherent solvent structure of pure 1,4-dioxane solvent with the diminishing of the water-dioxane clusters. The water-dioxane small clusters disappear in the mixtures at x dio > 0.7.