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The complex structures in the entire composition range of water-methanol mixture were studied by pyrene fluorescence probe. The results showed that the decrease rate of I1/I3, the pyrene scale for solvent polarity, exhibited clear dependence on the mole fraction (xm) range of methanol in the mixture, while the relative quantum yield of pyrene fluorescence showed a remarkable maximum at xm=0.18. These results revealed that in a wide range of 0.18xm0.75, the molecules of water and methanol mainly formed water/methanol (W/M) complexes (W5M1-5) and methanol/water (M/W) complexes (M6W2-4, M8W1-3), and a transition of "W/M→M/W" complexes would occur at xm≈0.50. This notion provides a conjuncture to reconcile the two existing formulations about water-methanol complexation.