Carriers balance is essential in obtaining efficient polymer-light emitting diodes (PLEDs). However, for most electroluminescent polymers the injection and transport of holes are much faster than those of electrons, leading to imbalanced carriers in emission layer and degraded efficiency. Conventionally, an electron-injection layer is inserted between emission layer and metal cathode to promote electron injection/transport to improve carriers balance and emission efficiency. However, theoretically inserting a hole-buffering layer between anode and emission layer is also effective to balance the carriers and emission efficiency. In this work we have prepared two new pyrene-containing polyimines (PPI-1, PPI-2) and applied them as hole-buffering layer (HBL) to enhance emission efficiency of polymer light-emitting diodes. Both PPI-1 and PPI-2 contain azomethine groups in the main chain, which can lower the HOMO levels to improve hole-buffering capability. Multilayer PLEDs have been successfully fabricated using spin-coated PPI-1 and PPI-2 as HBL (ITO/PEDOT:PSS/HBL/SY/LiF/Al). The optimal maximum luminance and maximum current efficiency of the device with PPI-1 as HBL were 19,324 cd/m2 and 7.9 cd/A, whereas those based on PPI-2 were 22,401 cd/m2 and 8.0 cd/A, respectively. Both are superior to the device without the HBL (10,818 cd/m2, 2.5 cd/A). On the other hand, PPI-2 surpasses PPI-1 in terms of emission color purity. The results indicate that insertion of hole-buffering layer is effective in enhancing efficiency of PLEDs and both PPI-1 and PPI-2 are potential hole-buffering materials to enhance device performance of electroluminescent devices.