Abstract: Using the self-designed plasma generator, the development of thermal plasma jet under atmospheric pressure was analyzed through experiments. The air discharge characteristics at atmospheric pressure were simulated. The distribution of velocity and temperature fields for plasma arc was obtained through the direct coupling calculation of electric field, magnetic field, temperature field and velocity field. The effect of different gaps on discharge results was analyzed. The results show that when the discharge gap increases from 1.5 mm to 3.5 mm, the thermal jet velocity increases from 41.5 m/s to 62.4 m/s, and the temperature decreases from 3 650 K to 1 960 K. If the gap is too narrow and the temperature is too high, the electrode will be ablated and its service life will be affected.