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In this paper, initiation and growth behavior tests of small fatigue crack in laboratory air and aqueous 3.5% NaCl were conducted using non-corroded and pre-corroded SENT specimens for 2024-T62 Aluminum alloy. In order to compare with the corresponding small cracks, large crack growth tests for non-corroded and corroded specimens with different prior corrosion times were performed. Variation of pre-corrosive pit sizes with corrosion time was also studied. The results show that for fatigue specimens with pre-corrosive pits, small cracks initiated from the corrosion pits in both laboratory air and aqueous 3.5% NaCl, and initiation lives of small cracks (a≤60μm) are below 25% of total fatigue lives. For non-corroded fatigue specimens in laboratory air, small cracks initiated naturally from voids of the material, and initiation lives of small cracks (a≤25μm) are below 20% of total fatigue lives.