The relationship between ζ-potential and surface defects of micro-nano sized hexagram-like α-Al2O3 particles was investigated in this paper. The 2D α-Al2O3 particles was prepared by the phase transformation of gibbsite precursor by the following steps during calcination in air: Al(OH)3 → AlOOH→a-Al2O3 → θ-Al2O3 → α-Al2O3. Resulting from the varied intensities of surface defects, as-prepared α-Al2O3 samples have different Eg values around 4.5 eV, which is much narrower than that of bulk α-Al2O3. While benefiting from the interface reaction between surface > AlOH0 and water (>AlOH0 + OH−⇋ > AlO− + H2O), as-prepared α-Al2O3 suspensions can reach their specific pHE values after stirring for 8 h at room temperature. And the measured IEP values of Al2O3-1250°C-2 h, Al2O3-1250°C-3 h, and Al2O3–1300 °C-3 h, which remain 2D morphology, are 7.96, 8.67, and 8.86, respectively. This study is significant and useful for making the industrial applications of α-Al2O3 valid.