A double layer organic thin film electroluminescent device (DLD) (ITO/SA/Alq3/Al) and two three layer devices (TLD) (ITO/SA/PBD/Alq3/Al) with different thickness of PBD have been prepared. Here SA is a kind of derivative of styrylphenylamine. The EL spectra, current voltage, brightness voltage and efficiency of the devices have been investigated. It was found that TLD with 35 nm PBD emitting both from Alq3 and SA, and DLD and TLD with 10 nm PBD have higher current density and brightness over 2 orders than TLD with thicker layer PBD, though that the quantum efficiency of three decives are almost the same. The quantum efficiency of devices with SA are 0.09~0.1%, much higher than the single Alq3 layer device (0.04%). Energy band models were schemed to well complain the EL performance of the devices. The stability against air was studied also. After put in air for ten months, the brightness of the devices is about 50% of its initial one.