The invention discloses a device and a method used for measuring the dielectric constant and the dielectric loss of samples under low temperature and high pressure. The measurement device comprises a pressure cell, a Be-Cu piston-typed press, a variable temperature system, a data collecting system and a data processing system; the method of the invention used for measuring the dielectric constantand the dielectric loss of the samples under low temperature and high pressure is characterized in that the Be-Cu piston-typed press applies quasi-hydrostatic pressure to the pressure cell; the variable temperature system and a dielectric property testing device are adjusted; by using a temperature measuring device and the dielectric property testing device to collect the capacitance and the dielectric loss of the samples under the temperature change and the frequency change of the samples, the variable frequency and variable temperature scanning curve line measurement is finally realized by the processing of a PC machine; the method of the invention changes the temperature and the frequency of the dielectric constant simultaneously, realizes the variable frequency and variable temperature scanning curve line measurement, and can research the effects of the quasi-hydrostatic pressure on the dielectric property of the ferroelectric samples by changing the externally applied quasi-hydrostatic pressure.