ZnO vertical well-aligned nanorods were grown on AlN/sapphire by using metal-organic chemical vapor deposition. We first observed the ZnO net-like structures under the nanorods. The different strain was determined in these two layers by using double crystal X-ray diffraction, Raman spectra, which revealed that the nanorods were relaxed and the net-like structures were strained. The optical properties of two layers were measured by using the cathodoluminescence and photoluminescence and the shift of UV peaks was observed. Moreover, the growth mechanism of the ZnO nanorods and the net-like structures is discussed.