In order to study the effect of different hole injection layers on the performance of flexible OLED devices, HAT-CN, PEDOT∶PSS and PEDOT∶PSS/HAT-CN were used to prepare flexible OLED devices and measure their performance parameters. The device structure is PET/ITO/HIL/TAPC (60 nm)/CBP∶Ir(ppy)3 (20 nm, 10%)/TmPyPB (45 nm)/Liq (2 nm)/Al (100 nm). PEDOT∶PSS was prepared by spin coating, and the other organic layers and cathode were prepared by vacuum evaporation. The results show that the flexible OLED device with PEDOT∶PSS/HAT-CN composite film as hole injection layer has the best performance. The maximum current efficiency and power efficiency can reach 84 cd/A and 76 lm/W. The research shows that the surface of the flexible substrate modified by PEDOT∶PSS has better continuity and smoothness, so that the phenomenon of leakage and short circuit is reduced; meanwhile, the composite film of PET/ITO/PEDOT∶PSS/HAT-CN has a higher transmittance in green light band, which can improve the extraction efficiency of the device. Moreover, the injection of carriers in this device is in balance, increasing the compound probability of electrons and holes.