To promote the development and application of MgO-based single component alkali-activated slag materials（AASM）， MgO was used as activators or along with sodium silicate for elucidation of their effects on hydration microstructure and mechanical properties of single component AASM. Moreover， micro-mechanical properties were also analyzed by nanoindentation. Results show that the formation of Mg（OH）₂ after MgO contacted with water provides an alkaline environment， which induces the dissolution of slag. While the dissolution of sodium silicate further elevates the solution pH value and accelerates the fracture of Al—O and Si—O chemical bond as well as the release of Ca²⁺. This forms a double strengthening effect to promote the hydration of slag. In addition， the composite activator of MgO and sodium silicate produces more abundant hydration products. Pore structure analysis reveals that AASM has the lowest porosity and the least harmful pores by using the combined MgO and sodium silicate to activate slag. More hydration products with high elastic modulus are produced in combination with MgO and sodium silicate， thus contributing to the increase in micro-mechanical properties.