The invention discloses a planar electrode structure suitable for vacuum surface flashover, including an insulating fastener, a high voltage electrode, a ground electrode, an insulating bracket and aninsulator to be measured. A groove is arranged in the middle of the upper part of the insulating bracket, and the insulator to be measured and the groove are matched. The high voltage electrode and the ground electrode are in surface contact with the insulator to be measured. The high voltage electrode and the upper part of the ground electrode are connected with a pressing mechanism, and the clamping mechanism keeps the close contact with the insulator to be measured. The pressing mechanism includes the insulating fastener, an electrode fixing bolt I and a fixing bolt I. The electrode fixingbolt I is connected with the insulating fastener. The fixing bolt I is matched with the electrode fixing bolt I. The insulating fastener is connected with the insulating bracket at the lower part through a support piece. The planar electrode structure has the advantages of simple structure, good discharge stability, small influence of the gap electric field of the vacuum surface flashover, reduction in the discharge dispersion of the vacuum surface flashover, high reliability, strong operability, long service life, and small influence of the electrode fixing and the insulating support structure on the gap electric field.