Temperature dependence of persistent internal polarization of ZnCdS phosphors has been stu-died. Measurement of thermally depolarized charges after the polarization shows the presence of electron traps of 0.60 eV and 0.78 eV in depth. This result accounts for the temperature depen-dence of the rate of dark polarization. Also, the experiment indicates that the polarization hass the peakvalue when it occurs at temperatures around 60°C, and above this temperaturethe polari-zation drops to a much smaller value. The characteristics may be explained with a reduced barrier model in consideration of the hole distribution.