It is necessary to enhance DC electrical insulation performance in power equipment such as DC gas insulated switchgears (DC-GISs) for the introduction of DC power transmission systems. In gas-solid DC composite insulation systems, the gas conductivity is strongly affected by the sources for the charge carriers such as the electrode roughness and partial discharges. In particular, two types of conductivity conditions are considered; (1) the higher conductivity value in SF₆ gas than that in solid insulator, that is, gas-conductivity-dominant (GCD) condition under which the source of charge carrier such as partial discharges and electron emission due to surface roughness. (2) the higher conductivity value in solid insulator than that in SF₆ gas, that is, solid-conductivity-dominant (SCD) condition under which natural ionization and charge injection from electrode. In this paper, the electric field distributions in SF₆ gas around epoxy-spacer in DC-GISs were calculated at DC switch-on, DC steady-state and DC polarity reversal (DC-PR) conditions, while changing the parameters of the spacer angle and thickness under both GCD and SCD conditions. Accumulated surface charge on solid insulator and resultant DC electric field transition were investigated in consideration of the difference between GCD and SCD conditions. In addition, we discussed the relationship between the accumulated charge density under DC steady-state conditions and the electric field distribution at DC-PR condition. As a result, in the case of GCD conditions, the electric field is concentrated in epoxy-spacer under DC steady-state conditions and the location of maximum electric field changes with time due to significant accumulated charge on epoxy-spacer. On the other hand, in the case of SCD conditions, DC electric field distribution around epoxy-spacer hardly changes due to slightly accumulated charges. In addition, in the case of GCD conditions, the significantly accumulated charges under DC steady-state conditions can be a critical parameter in determining the maximum electric field at DC-PR conditions. From the view points of the amount of accumulated charge under DC steady-state conditions and electric field stress at DC-PR conditions, electric field distributions under GCD conditions can be more distorted than that under SCD conditions.