<p>Important basic parameters for the study of non-equilibrium plasmas are the electron number density <i>N</i>_<i>e</i>, electron temperature <i>T</i>_<i>e</i> and heavy particle temperature <i>T</i>_<i>h</i> of non-thermal arc plasmas at atmospheric pressure. In this study, based on electrical diagnosis, array fiber-emission spectroscopy, and M-Z holographic interferometric optical diagnosis, non-thermal arc spatial parameters were diagnosed, particularly the large parameter gradient distribution due to the interaction between the non-thermal arc and cold air. The results show that the non-thermal arc plasma is in a partial LTE state when the current is less than 1&#xa0;A and the electron number density reaches 10¹⁶cm^− 3. For Ar/N₂ arc discharge in pLTE state, the volt-ampere characteristics are decreased, and the arc column cooling is strengthened after the increase of gas flow rate, resulting in the increase of discharge voltage and electric field strength in the arc column region, and the pLTE plasma deviates from the local thermodynamic equilibrium. The maximum values of electron temperature and heavy particle temperature are concentrated in the near cathode region of the arc column, and the radial distribution is Gaussian. The number density of electrons in the core region of the non-thermal arc is ~ 10¹⁶cm^− 3, and its maximum value is distributed near the cathode region and decreases along the axis, while radial distribution is in line with the bell-like distribution. When the distance from the axis to ~1&#xa0;mm, electron density rapidly decreases to the center range of 1 ~ 2 orders of magnitude.</p>