A new rare earth complex Tb(p-MBA)_3phen has been synthesized,and the electroluminescence(EL) and photoluminescence(PL) characteristics of the Terbium complex and PVK system were investigated.In the EL spectra,the emission of PVK is completely restrained,and only the green emission come from Tb~(3+) can be observed;while in the PL spectra,obvious emission of PVK can be seen besides the emission of Tb~(3+).It is because of the different mechanism of electroluminescence and photoluminescence.The luminescent characteristics of the device were preliminarily discussed by measuring and analyzing the emission and the excitation spectra of the Tb complex and the mixture of the Tb complex dispersed in PVK film.Two mechanisms of the emission were proposed.The energy of Tb complex may partly come from PVK through Frester energy transfer process,and another possibility is the electrons and holes may be captured by Tb complex directly.