The transient fluorescence characteristics and mechanism of Alq3 compound films have been studied.It has been found that the fluorescence peak wavelengths of Alq3 compound films blueshift and the fluorescence lifetimes are shorter than those of Alq3.The reductions of the fluorescence lifetimes of the compounds are attributed to the quenching of host molecules and the blue shifts of the fluorescence peak wavelengths are asigned to the interactions between Alq3 and the host molecules.