The effect of energy transfer is an important phenomenon in luminescence material. Energy transfer between 5, 6, 11, 12 -tetraphenyltetracene(Rubrene) and N, N'-bis-(1-naphhyl)-N, N'-diphenyl-l,l'-biphenyl-4,4'-diamine(NPB) has been studied in organic thin film by time-resolved spectra and emission spectra. The dynamics equations were discussed to explain these process, andthe solutions obtained can be compared to the computer simulation with the experimental results. White light emission can be produced by adjusting the concentration of Rubrene in photoluminescence. However, with devices of structureITO/CuPc/NPB:Rubrene/TPBi/Alq/Mg:Ag with a blocking layer, the white lightemission can not be obtained by adjusting the concentration of Rubrene in electroluminescence. The mechanism of energy transfer has some difference in electricfield.