Biomass combustion for heat and power generation is one of the best ways for substituting fossil fuels. It is necessary to develop in situ temperature and emissivity measurement technology for biomass volatile flame. In this study, combustion experiments on three biomass pellets of pine wood, rice husk and fir wood were carried out in a laboratory biomass burner at two A/F flowrates. A multi-wavelength radiation thermometry method was proposed to calculate temperature and wavelength-dependent emissivity based on Rayleigh approximation. The results showed that the temperature and emissivity of pine wood combustion were higher than those of rice husk and fir wood volatile flames. Though the emissivity of rice husk was less than that of fir wood, the temperature of rice husk combustion was higher than that of fir wood due to the latter’s higher moisture content. The temperatures measured by the spectrometer system agreed well with the thermocouple data. The normalized emissivities of the three different biomass show the same trend, indicating the radiative properties of biomass volatile flames do not change with biomass species and combustion conditions.