In the article the parameters of an electrostatic filter were considered, including the level of the electric field intensity and the magnitude of the breakdown voltage. A computer simulation of the electric field between flat parallel electrodes with different potentials was performed. The change pattern of the electric field at the penetration of electrically conductive soot particles is considered. With the help of the “ANSYS” software complex, the pattern of change of the electric field intensity between these electrodes was investigated depending on the concentration of particles between them. A computer model that simulates the creation of a maximal level of electric field intensity in a symmetric electric field with a fixed air gap is proposed. The decrease of the level of the breakdown voltage at these electrodes at the placing between them of elements simulating diesel soot particles with average sizes mentioned in the literature is estimated. According to the simulation results, it was determined that the presence of particles of electrically conductive soot significantly influence on the electric field pattern, due to which a local change in the pattern of the resultant field intensity occurs. With aim of confirming of the obtained data the experimental studies have been carried out for determination of the breakdown voltage between the electrodes which form a symmetric electrostatic field.