In this study, a novel AlGaN/GaN power rectifier with an integrated lateral composite buffer diode (IBD-Rectifier) for reverse blocking capability improvement is proposed and investigated by Sentaurus simulations (this paper includes only simulated data and no real experimental result). AlGaN buffer layer under the anode is adopted to realise great high reverse blocking capability. A minimum turn-on voltage of 0.6 V and a maximum breakdown voltage (BV) >1.3 kV are simultaneously obtained in the IBD-Rectifier, resulting in a high Baliga's figure of merits BV 2/R on,sp (R on,sp is specific-on resistance) of ∼3000 MW/cm2. In comparison with MIS-gated hybrid anode diode and conventional schottky barrier diode, the IBD-Rectifier delivers an excellent theoretical method to achieve superior performances in high-efficiency GaN power applications.