An atmospheric-pressure helium plasma generated in a 2.45-GHz microwave-induced cylindrical plasma torch has been investigated. The atmospheric-pressure helium plasma can be ignited at a microwave power of less than 400 W and sustained at as low as 100 W, at a gas flow of 50 L/min. The electron temperature , electron density , and gas temperature measured by optical emission spectroscopy are 0.28–0.5 eV, – , and 1000–2000 K, respectively, at a power of 200–400 W and a gas flow rate of 20–50 L/min. In addition, it is noted that (rotational temperature) for these experiment parameters. These results show that the helium plasma generated in this atmospheric-pressure plasma torch is in partial local thermodynamic equilibrium (pLTE).