The green phosphorescent organic light emitting diode (OLED) device with the structure of ITO/MoO₃(40nm)/NPB(40nm)/TCTA(10nm)/CBP:Ir(ppy)_2acac(14%)(30nm)/BCP(10n m) /Alq₃(30nm)/LiF(1nm)/Al(100nm) were prepared.By measuring the luminance,tem perature,current and efficiency and other parameters under different voltages,the thermoelectric breakdown characte ristics of the device are analyzed and studied by Wagner thermal breakdown theory and space-charge limiti ng current model.So that we can find a way to improve the lifetime of OLED device.The results show t hat when the voltage is small,with the increase of time, the temperature of the device is basically stabilized at 20℃ the luminance of the device is basically stabilized at 80－400cd/m²,and the curre nt efficiency of the device is basically stabilized at 40－60cd/A.When the vol tage is high,with the increase of time,the temperature of the device rises from 22.16℃ to 35.91℃ in 114s,the luminance of the device is reduced from 17380cd/m^2to 7585cd/m²ⁱⁿ 193s,and the c urrent efficiency of the device is reduced from 0.122208cd/A to 0.0545152cd/A in 106s.That is because when the voltage is small,the carrier has less energy,and the migration speed is slow,which makes the current of the device sm aller and also makes less heat generation so the heat can be sent out in time.However,when the voltag e is high,the movement of electrons and holes is intensified and the current ins ide the device also increases rapidly, the heat generation is greater than the heat dissipation so the temperature rise s rapidly.The device finally appears the thermoelectric breakdown,so that the performance of the dev ices is reduced.It can be seen that the heat dissipation of OLED devices has a very important impact on the breakdown.A good heat dissipation condition can reduce the probability of thermoelectric bre akdown of the device,and then extend the lifetime of OLED devices.