Spectroscopic diagnostic technique are applied for the determination of excitation temperature Texc and electron density in Air - Acetylene premixed laminar flame. A group of FeI spectral lines has been used to estimate Texc using Boltzmann plot. Electron number density was determined from atom ion line pairs for Cd and Zn using Saha - Boltzmann equation after substitution the obtained value of excitation temperature. The obtained result of temperature show that the populations of energy levels follow Boltzmann's distribution law.