The disclosure provides a wide-temperature-range radiation-source-excitation scintillation crystal fluorescence measurement system and method. The measurement system comprises a refrigerator, a radiation source and a PMT test system. The refrigerator includes a cold stage, a low temperature chamber, a temperature controller and a temperature probe; the cold stage is arranged at the upper part of the refrigerator body; a to-be-measured crystal sample is arranged at the cold stage; the low temperature chamber is arranged outside the cold stage; and the temperature controller is used for adjusting the refrigeration temperature of the refrigerator, so that the temperature of the cold stage satisfies the required temperature of the to-be-measured crystal sample. A first temperature probe is connected to the cold stage; a second temperature probe is connected to the surface of the to-be-measured crystal sample; a third temperature probe is connected to the PMT test system and is closely attached to the side of a photocathode glass tube wall, extending into the low temperature chamber, of the PMT test system; a photocathode of the PMT test system is responsible for collecting the scintillation fluorescence of the to-be-measured crystal sample, converting the collected optical signal to an electric signal, and outputting the electric signal to the PC side. According to the disclosure,since the PMT test system extends into the low temperature chamber of the refrigerator, the efficiency of fluorescence collection is improved.