We investigate the magnetoresistance(MR) in double-quantum-well OLED through changing doping concentration of C-545T.The device was fabricated as follows:ITO/2T-NATA(21 nm)NPBX(50 nm)/Alq3:C-545T(20 nm)/Alq3(3 nm)]2/Alq3(17 nm)/LiF(0.5 nm)/Al.After studing the MR of double-quantum well OLEDs at different doping concentrations(1.5%,4%,6%) at room temperature and the same magnetic field,the results shows that the resistivity(ρ) decreases with increasing the C-545T concentration under the same magnetic field strength and the same voltage.The device with 6 % C-545T is obtained with resistivity of 42.24×103 Ω·m at an applied voltage of 10 V and the magnetic field of a 0 mT.MR gets smaller remarkably with reducing C-545T concentration at the same magnetic field strength.The device with 1.5 % C-545T is obtained with MR of-18.36% at the magnetic field of 50 mT.The negative MR is observed in our devices.