Mg doped ZnO (MZO) thin films were prepared by magnetron sputtering and laser induced breakdown spectroscopy (LIBS) were characterized by Q-switched nanosecond 1064nm Nd:YAG laser pulse. Element characteristic spectral lines from MZO thin films with Mg concentration of 0.1 at%, 0.26 at% and 0.49 at% are illustrated by LIBS system. The results show that Mg (I) emission lines are observed corresponding the relatively high excitation with increasing Mg doped concentration. It can be mainly interpreted as more crystallization planes produced by high Mg doping concentration radiate different atomic spectral lines. The results are in relative agreement with XDR patterns. We calculated the electron density of 8.08×1022 cm-3, 7.70×1022 cm-3 and 7.99×1022 cm-3 inferred by measuring the Starkbroadened line profile. The electron temperature of 21875.85 K, 42941.49K and 28985.51K was determined using the Boltzmann plot method through the acquired data.