A double layer electroluminescent (EL) device is constructed by using a lundnescent layer, 8-hydroxyquinoline aluminum (Alq3 ), and a hole-transport layer,microcrystul diamond film. The EL spectrum, the J-V and B-V characteristics have been measured, and the quantum efficiency has been calculated. It .is showed that the current of the device with diamond film is lower than that of single Alq3 layer device but the quantum efficiency is higher than single layer device. A energy band model has been estublished, and the exprimental results has been well complained.