Laser-induced breakdown spectroscopy(LIBS) was used to in situ monitor the concentration of alkali elements in combustion environments. Particular efforts were made to optimize the temporally resolved spectra of Na and K elements. Calibration curves were constructed by relating the intensities of the specific lines to the corresponding elemental concentrations. The detection limits of Na and K elements were found to be temperature-dependent. The results indicate that LIBS can be a powerful tool for in situ monitoring Na and K concentrations in combustion environments.