High-strength ultrathin cover glass is an important part of electronic information products, and chemical strengthening (ion-exchange) is the main technological approach to improve the mechanical properties of ultrathin cover glass. During ion-exchange, stress relaxation (structural relaxation) can easily take place, making it difficult for chemically strengthened glasses to simultaneously achieve high compressive stress, large depth of layer, and high Vickers hardness. To overcome this issue, two-step ion-exchange was developed to strengthen aluminosilicate glasses. Effects of molten salts, ion-exchange temperature and duration on the distributions of stress layers and Vickers hardness were investigated. Results demonstrate that high compressive stress, large depth of layer, and high Vickers hardness can be simultaneously achieved via two-step ion-exchange. After ion-exchange, the compressive stress of the glass is over 900 MPa, the depth of layer is over 70 μm and Vickers hardness is over 7.2 GPa.