Dependence of light intensity on temperature is investigated for a dual emission (Ba, Sr)3MgSi2O8:Eu2+, Mn2+ phosphor with a high quantum efficiency. The dual emission spectrum, which matches the photosynthetic absorption spectrum and photosynthetic effective spectrum, is composed of 660 nm-peaked red band and 430 nm-peaked blue band. Thermal quenching of both red and blue band emissions is observed from 293 K to 473 K. The peak position for red exists blue-shift with temperature increasing while that for blue remains unchanged. This phenomenon is most likely associated with a multi-lattice site occupation of Mn2+ and electron-phonon interaction in the host lattice involved in an energy transfer from Eu2+ to Mn2+. The results provide further understanding of energy transfer between Eu2+ and Mn2+ and thermal quenching property of (Ba, Sr)3MgSi2O8 and reference in the application of this phosphor and the fabricated bio-lighting devices.