Abstract: To reduce the jitter of the direct current self-breakdown voltage, and not affect the self-breakdown voltage as much as possible, an auxiliary discharge electrode structure with an auxiliary discharge needle implanted in the cathode center is designed based on the discharge gap of the annular electrode. The influence of the diameter, length and top chamfer of the auxiliary discharge needle on the field distortion is studied by electric field simulation. The direct current self-breakdown characteristics of the gas gap without and with auxiliary discharge needle in dry air and SF₆ gas are studied by experiments. The results show that the smaller the diameter and the longer the length of the auxiliary discharge needle, the weaker the shielding effect of the electrode ring on the electric field, the stronger the field distortion intensity; the influence of the implatation of auxiliary discharge needle on the direct current self-breakdown of SF₆ gas discharge gap is small, and with the increase of the field distortion coefficient, the percentage drop of self-breakdown voltage of dry air at the same air pressure is 2-3 times that of SF₆ gas; the auxiliary discharge needle has a beneficial effect on the breakdown stability of dry air and SF₆ gas discharge gap under the condition of direct current , the dispersion reduction percentage is about 25% higher than that without auxiliary discharge needle.