Microwave measurement method and device applicable for determination of physical properties (density, concentration of mixtures, water content, etc.) of different dielectric liquids located in tanks (technological tanks, measuring cells, etc.) are considered. Waveguide is done as a coaxial waveguide, a fixed frequency of a generator is chosen lower than a cut-off frequency of the coaxial waveguide for its lower wave mode H11. Generator of electromagnetic oscillations of a fixed frequency is connected with the waveguide at one of its end parts by a first coupling element while detector is connected with the waveguide at its second end part by a second coupling element. Register of amplitude of electrical field strength is connected with output of detector. Also device for measurement of physical properties of a dielectric liquid may contain a waveguide with a monitored liquid located in electromagnetic field of the waveguide at one of its end parts and with the same liquid with a reference value of its measured physical property at the other end part of the waveguide.