This paper reports the experimental investigation on the local thermal equilibrium (LTE) characteristics of 25 kW argon wall-stabilized arc plasma using spectroscopic method. The results show that the plasma is at least of PLTE in the experimental conditions, and basically of LTE when the pressure is larger than 0.05 MPa and the currents are higher than 50 A. The half-width is only dependent on the electronic density and independent on the plasma state.