This paper presents an experimental investigation on the measurement of temperature and emissivity in a 46 ton/h Municipal Solid Waste (MSW) incinerator using a spectrometer system and a flame image detection system. The spectroscopy analysis shows that strong Na (590 nm) and K (767 nm) emission occurs in the visible spectrum of the flame in the MSW incinerator, which demonstrates a typical nongray property of radiation. The two-color method is used to calculate the temperature and emissivity of the flame from the continuous spectrum and the visible flame image, and the results indicate that except for the Na (590 nm) and K (767 nm) emission lines, the continuous spectrum from the particulate medium in the flame meets the gray property. Since the strong but narrow Na and K emission lines deviate away from the central wavelengths of red (R) and green (G) in the spectral response curves of the CCD camera, the two-color method can be used to calculate the temperature and emissivity images by the flame image detection system. The preliminary experimental results show that these two techniques will be helpful for combustion research and monitoring in MSW incinerators.