Abstract: The characteristics of low-powered microwave plasma torch discharge are studied.The variation of excitation temperature with the observed height under different experimental conditions was measured by using double-line method.The emission intensities of Zri, Cd, Mg a-tomic and ionic lines were determined.The influence of experimental parameters on the excitation temperatures was also studied.The results show that the variations of emission intensities of analytes with observed height are in accordance with the excitation temperatures.They all have a maximum at the vertical height of 6～7 mm above the torch.The emission in the region of 5～10 mm above the torch is most intense, no matter for soft lines or hard lines.The emission profiles are not related to their excitation energies, but related to the optial structure of MPTdischarge.

Key words: MPT source, Excitation temperature, Emission intensity