The growth mechanism and characteristics of the nonpolar GaN/ZnO heterostructure grown on the r-plane sapphire substrate by using molecular beam epitaxy were studied. The crystal interaction between GaN and ZnO epitaxial layers was clarified by using transmission electron microscopy and X-ray diffraction. A new epitaxial relationship of ZnGa 2 O 4 (220)//GaN (101Ì...3Ì...) in the normal surface direction was obtained in the GaN/ZnO heterostructure. It was believed that the formation of ZnGa 2 O 4 (220) was due to the recrystallization of the ZnO layer with Ga atoms, which in turn resulted in the formation of semipolar-oriented GaN. In addition, the main optical transition in the GaN/ZnO heterostructure was attributed to the existence of the interface states and new ZnO:(Ga,N) alloys.