The temperature-dependent photoluminescence behaviour of chemical vapour transport (CVT)-grown ZnSe crys-tal is investigated. A new emission band appears when temperature is reduced to 155K. It is shown that the new emission band is strongly related to defect emission peaked at around 2.1 eV. The emergence of the new emission band is accompanied by decreasing emission intensity of free exciton, as well as redshift of defect emis-sion with temperature decreases. The activated energy of the defect state is estimated to be 60.6meV, which is approximately equal to the energy difference between the new emission and the Tree exciton emission at 155 K.