Emission spectroscopy is an important method for plasma diagnostics. The intensity ratio of spectrum lines at 763.51 nm and 772.42 nm is used to estimate the electron excited temperature of the thermal plasma jet under the low pressure plasma spray. Impact of different power levels and detection distance on the electron temperature in the thermal spray plasma jet under Ar/H2 flow rate of 40 L/min/15 L/min is investigated. Electron number density of the plasma jet is determined using stark broadening of Hβ , impact of changes of the detection distance is also studied. An increase in input power considerably increases the electron temperature, while it is found that electron temperature decreases with detection distance from nozzle exit increasing from 150 mm to 450 mm, and the increase of detection distance from l00 mm can remarkably reduce the electron number density. After that, there is little change of electron number density.