Microwave method for measurement of water content in a dielectric liquid is considered. The method provides independency of measurement results on the value of dielectric permittivity of a water-free liquid. A layer of a monitored dielectric liquid is sounded within a measuring section by electromagnetic waves in two measurements at fixed frequencies f1 and f2.Different values of water dielectric permittivity relate to these frequencies. As results of these soundings appropriate values ε1 and ε2 of dielectric permittivity of a water-containing liquid are determined by measured values Δφ1 and Δφ2 of phase shift of electromagnetic waves of the corresponding frequencies f1 and f2 after propagation of these waves through the layer of a monitored liquid. Water content is founded as a result of joint functional processing of ε1 and ε2. At least one of the frequencies f1 and f2 is chosen in microwave frequency range where frequency dispersion of dielectric permittivity of water takes place at this frequency.