Under the cyclic wet-dry conditions of 50% RH and 90% RH at 25 ℃, the spreading behaviors of micro-droplets were investigated in situ with the stereomicroscope with and without the electrochemical polarization. The results indicated that there was an unobvious influence of the wet-dry cycles on the formation and spreading of micro-droplets in a condition without the electrochemical polarization. Under the external polarization, with the advance of the wet-dry cycles, the areas covered with micro-droplets alternately expanded and dwindled, and the polarization current Ip and polarization resistance Rp changed impulsively. The maximum of Ip in each cycle increased gradually followed a reverse spreading changing rule. with the increase of the wet-dry cycles and the corresponding maximum of Rp Under cyclic wet-dry conditions, it showed a closed relation between the of micro-droplets and corrosion current. They were influenced and promoted with each other.