Abstract:The cumulative probability of lightning current amplitudes is one of the most significant parameters of lightning flash. Here presented are the statistical data of the first stroke current of lightning flash， collected by LLS (Lightning Location System) of ADTD type. Negative first strokes have traditionally been considered to produce the worst stress on the earth. The positive strokes have about the same median current value as the negative first strokes and longer fronts, thus producing less stress. However, their duration is longer than that of the negative strokes. Therefore, we estimate the first stroke current distribution in Chongqing using the empirical equations from the IEEE standards and the DL/T standards， respectively. It is found that the first stroke current distribution is changed with the polarity and the density of lightning stroke is different with the intensity of lightning current. Ｔhe LLS inferred peak current distribution estimate equation according to the Task Force recommendations into IEEE standards is effective, because the results according to the Task Force recommendations into IEEE standards fit more suitably to the statistical data than those according to the power team recommendations into DL/T standards.