Abstract: Based on the fact that the dielectric constant of water is even higher than that of constituents Of fluxes, a capacitance condenser for fluxes has been designed. Electrical capacitance of fused type and sintered type fluxes was measured and correlated with the actual moisture content. Throngh regression analysis, the measwring results can be expressed as sigmoidal functions.The bond between the surface of fluxes granules and water molecules play an important role in the dielectric method of moisture measurement, the weaker bond is, the higher sensitivity of measurement is. The saturated moisture contenthas a correlation with hygroscopicity of fluxes. The electrical capacitance method of measuring the moisture content of fluxes is highly sensitive, rapid and suitable for on site measurement.