A SF6 self-blast switching chamber belongs to a new generation of high-voltage switching devices, which take advantage of the auto-expansion principle and arc rotation to improve the switching performance on thermal and dielectric interruptions. The thermal behaviors between the arc plasma and the electrodes in the device are very complex to understand only through experimental studies. Since the late nineteen-eighties, significant progress has been made in computational methods describing the physical processes occurring in thermal plasmas. The final goal of a computer simulation on thermal plasmas is to predict the switching performance on thermal and dielectric interruptions from an engineering point of view. In this paper, we have conducted computations to predict the thermal and dielectric breakdown capabilities of a SF6 self-blast switching chamber from the results of the thermal behaviors during the entire switching process, such as a high-current period, pre-current zero period, and current-zero period. Through the complete work, the temperature of the residual thermal plasmas as well as the breakdown index after the current zero should be good criteria to predict the thermal and dielectric capabilities of the switching chambers.