A GaN/Si nanoheterostructure is prepared by growing wurtzite GaN on a silicon nanoporous pillar array(Si-NPA)with a chemical vapor deposition method.The temperature evolution of the photoluminescence(PL) of GaN/SiNPA is measured and the PL mechanism is analyzed.It is found that the PL spectrum is basically composed of two narrow ultraviolet peaks and a broad blue peak,corresponding to the near band-edge emission of GaN and its phonon replicas,and the emission from Si-NPA.No GaN defect-related PL is observed in the as-prepared GaN/Si-NPA.Our experiments prove that Si-NPA might be an ideal substrate for preparing high-quality Si-based GaN nanomaterials or nanodevices. A GaN / Si nanoheterostructure is prepared by growing wurtzite GaN on a silicon nanoporous pillar array (Si-NPA) with a chemical vapor deposition method. The temperature evolution of the photoluminescence (PL) of GaN / SiNPA is measured and the PL mechanism is analyzed .It is found that the PL spectrum is basically composed of two narrow ultraviolet peaks and a broad blue peak, corresponding to the near band-edge emission of GaN and its phonon replicas, and the emission from Si-NPA.No GaN defect-related Our experiments prove that Si-NPA might be ideal substrate for preparing high-quality Si-based GaN nanomaterials or nanodevices.