The electric field is formed in the isolation between electric charges located on the surface of the electrode in which they operate electric power. Electrostatic field is defined as a field that is caused by peaceful charge on the surface of electrodes, and within which there is no free charge in the area . In this paper we calculated the static electric field in GIS. The main feature of the GIS facility is completely shielding parts energized metal mantle where previously defined SF_6 gas is used as the insulating agent and as a means of extinguishing the arc. Sulfur hexafluoride (SF_6) is non-toxic, non-aggressive, chemically stable gas at atmospheric pressure and temperatures < 500 ⁰ C, colorless and odorless . This gas does not exist in nature, but is obtained by direct synthesis of fluorine and sulfur exothermic reaction liquid in a plant. Basic properties that enabled him to use and secure a leading position in the high-voltage circuit breakers are: high density, electronegativity , good thermal conductivity and a small time constant arc. For calculations of the static electric field and the dimensioning of insulation is necessary to know the number of occurrence and effects of the flashover/breakdown voltage in a gas such as: the occurrence of voltage corona, surface imperfections (roughness) of electrodes, the dust particles in a gas, a combination of gas and solid material of the insulator, and the presence of moisture. Field calculations are performed in Maxwell. Maxwell is electromagnetic field simulation program designed for 3 - D and 2 - D analysis of electromagnetic and electromechanical devices .