The requirements for increasing the switching capacity of SF6 circuit breakers, dictated by power grid companies due to the increase in rated short-circuit currents in networks of 126 kV and above, are difficult to satisfy. Firstly, the material, resource, and financial costs are significant, and secondly, before creating a prototype circuit breaker or upgrading an existing one, it is necessary to calculate the physical processes of arc extinguishing occurring in a high-voltage SF6 circuit breaker arc interrupter. The latter is reduced to the problem of modeling the interaction between the arc and the non-isothermal SF6 gas flow. This paper investigates this problem in a numerical software package, taking into account the arc in the form of a thermal heating source, based on experimental data on measuring the temperature of the arc during the breaking of a symmetrical short-circuit current of 10 kA. The calculations were carried out during the breaking of a 126 kV SF6 circuit breaker. Calculations of changes in the pressure and mass flow in the under-piston area, and the speed and temperature, depending on the contact movement, are given. The model of the arc interaction with the SF6 flow was used to simulate the symmetrical short circuit of a 25 kA current.