The test results of the properties of the unactivated CaF 2 scintillation crystal detector is reported. The energy response of a small size CaF 2 crystal and a large CaF 2 crystal detector, which will be used in the Ca 48 Double Beta Decay (DBD) experiment, to gamma rays and an electron beam from 6 to 10 MeV was tested. The results indicate that the linear energy response range can be extended to 10 MeV for the large CaF 2 detector. Meanwhile, the relation of the energy resolution to the incident particle energy is represented by E−1/2 (MeV) . (It is anticipated that the energy resolution at 4.27 MeV will be about 9%.)