It is known, that conductivity of liquid media as well as biological objects directly related to the mobility of ions, which in turn depends on Electric field strength. This article describes general principles and applications of method and hand-made conductometry device for measurement conductivity of a single biological cells and liquid media in pulsed Electric field with rising strength. The device allows to determine the conductivity in the range 0. 1-105 μ S/cm (with an error about 3%) in the field strengths 0-10 kV/cm, pulse duration 50 μ s, repetition period 5-10 s. Conductometric measurements were carried out on mouse and cow oocytes in 0. 3 M solution of sucrose and some 0. 3M aqueous solutions: xylitol, sorbitol, mannitol, glucose, sucrose, conventional distillate and deionized apyrogenic water. It was found that with rising in the field strength, the conductivity of cells first increases gradually and almost linearly in the range 0. 2-1. 3 kV/cm, and then sharper and finally exponentially, with strength more 2. 8 kV/cm and 3. 3 kV/cm for mouse and cow oocytes respectively, i. e., Electric breakdown of the cell membrane occurs. The conductivity of liquid media is almost independent of the field strength, but small variations in some media have shown the presence of conductive impurities in them, which are absent in the solvent. Thus, the cell conductivity changes in rising field strength can detect and investigate all stages of membrane electroporation (reversible and irreversible Electric breakdown) and the method can serve for estimating the purity of the initial reagents as well as quality control of other liquid media.