The invention discloses a new method for judging an optimal clarification area of float glass. High-temperature viscosity and surface tension test technology of glass melt is adopted. The relationship among Redox number, high-temperature viscosity and surface tension is accurately represented by testing properties such as high-temperature viscosity, surface tension and the like of the glass melt of different Redox numbers, wherein the Redox range that the high-temperature viscosity and the surface tension are synchronously small is an optimal glass clarification area range, so the method provides basis for determining the optimal glass proportioning parameters. The method is simple, high in test efficiency and intuitive and accurate in optimal clarification area judgment of the float glass, can ensure the production quality of the float glass, and is particularly suitable for judgment of the optimal clarification area of the float glass and preparation of the float glass.