We report the effect of N-2 partial pressure on the structure of MgO thin films deposited on Si(100) substrates by radio frequency-magnetron sputtering in Ar+N-2 mixture. The films were evaluated using x-ray diffractmeter. As increasing N-2 partial pressure, the intensity of (200)(MgO) reflection increased and saturated above partial pressure of 4.4X10(-1) Pa, which corresponds to N-2 flow late of 3 sccm. Effect of N-2 gas on the structure of MgO thin films were investigated by plasma emission spectroscopy. The increase of the optical emission intensity of NH spectrum results in the increase of intensity of (200)(MgO) reflection. We found the strong relationship between the emission intensity of NH spectrum and intensity of (200)(MgO) reflection.