The device structure:ITO/O-PPV/CuPc/Alq_3/Al,was fabricated,which the films of poly 2-methoxy-5-nonyloxy-1,4 phenylene vinylene (O-PPV) were treated with two ways:drying in vacuum for 15 hours and no drying,respectively.The results show that the electroluminescence (EL) of the sample cell with drying O-PPV film comes from the emission of O-PPV and the intensity of Alq_3 is greatly improved in undrying O-PPV film with the same applied voltage (12 V) due to the hole-electron recombination area changing.It is evidence that the transport property of the carrier with un-drying O-PPV film is faster than that of drying film.