Abstract: There are statistical parameters in long air gap discharge. Mathematical statistics and finite element simulation were both employed to research deeply on the discharge characteristics. Statistical results indicate that there’s a slightly influence of grounding rod height on the 50% discharge voltage of rod-rod air gaps; breakdown time is almost higher than the wave front time with 20/2 500μs switching impulse and it is lower than the wave front time with 80/2 500 μs; the distribution of discharge voltage in 10 m rod-plane gaps obeys the normal distribution; and the V-t characteristics of rod–rod gaps is lower than that of rod-plane. Calculation results indicate that nonuniform coefficient of electric field increases with increasing gap distance; the ratio of gap distance and nonuniform coefficient also increases with the gap distance but tends to level off, indicating a saturated discharge voltage with gap distance. The work conducted in this paper can provide preference to the insulation coordination designation of UHV transmission lines.