The effect of MgF2 and ZnO as additives on the microstructure evolution of a lithium aluminosilicate glass-ceramic is studied by X-ray powder diffraction and X-ray absorption near edge structure. The changes of main, secondary phase development and morphology under different additive concentrations are responsible for the variation in flexural strength. The decreased flexural strength (> 50 %) of MgF2-bearing samples can be attributed to the non-uniform microstructure, while the increased flexural strength of the ZnO-doped samples might be due to the decreased residual stress resulting from a reduction of viscosity. In addition, the structural role of Zn ions is changed under different phase evolutions. For highly crystalline samples with commercial-like composition, Zn ions tend to have spinel-like local environments; while in a simplified composition, Zn ions favor hexagonal ZnO-like surroundings. The appearance of significant multiple scattering peaks in the near edge structure indicates Zn ions usually presented in an ordered local environment in high doping level samples (> 1 % ZnO or MgF2).