A measurement system and mathematical procedure are developed for determining the quantum efficiency of luminescent materials. This technique based on standard photoluminescence DARSA PSI 5100 system (Diode Array Rapid Scan Analysis, Professional Scientific Instrument Co, Korea) or any other that allows measure the emission and excitation spectra, is applied to conventional phosphor powders. The system described is tested for excitation in the near-UV and visible regions, but can be applied to higher energy excitation (UV), as well as lower energy excitation to near-IR, with the appropriate photodetectors and optical filters. The system was tested on standard phosphors and on the new compositions. The accuracy of this measurement technique is acceptable for express analysis of quantum efficiency of luminescent materials.