Radiofrequency resonator method for level measurement of a dielectric liquid in a reservoir is considered. The method is characterized by independency of measurement results on the value of dielectric permittivity of a liquid. The method is realized via application of two co-axial sections of TEM (Transverse ElectroMagnetic) transmission lines. In one of them both parallel conductors of the two-wire line section are installed vertically in a reservoir with a monitored liquid. This transmission line section is done hollow along all its length. Inside this cavity serving as an outer conductor of the coaxial line section, a wire is coaxially installed serving as the inner conductor of this section of coaxial line. The sections of coaxial line and two-wire line have horizontal parts of fixed equal length at their lower ends. These horizontal parts are filled in by a liquid fully along all their lengths and are drained under coming in of a liquid into a reservoir and its removal from a reservoir accordingly. The TEM line sections are high frequency resonators. Their resonant frequencies of electromagnetic oscillations are measured. Level of a liquid in a reservoir is determined as a result of joint functional processing of these frequencies. This result is independent on the value of dielectric permittivity of a monitored liquid.