This invention relates to a method for identifying air excitation flow and airdrop faults correctly in the protection of high voltage transformers, which selects two watching windows at current waveforms, then utilizes the current in one of the windows to forecast a sine wave, utilizes the probability theory to compute the relative coefficient of the sine wave sequence and that of the windows to differentiate airdrop transformers and the fault ones by the relative coefficient to reach the aim of quickly excising the fault air transformers.