Novel behaviors arising from the coupling between the built-in surface electric field,piezoelectricity, electron–hole pairs and external light beam were observed in GaNnanorods. An increase in the optical excitation density resulted in a blueshiftin the photoluminescence spectra and a redshift in the frequency of the GaNA1(LO) phonon. The underlying mechanism was attributed to the screening of the built-in surfaceelectric field by photoexcited carriers and, through the converse piezoelectric effect, areduction in the internal strain. The existence of the built-in surface electric field in GaNnanorods was confirmed by scanning Kelvin probe microscopy. Our results firmly establishthe existence of the photoelastic effect in GaN nanorods. In addition to underpinningthe principle for applications in nanophotonic devices, this discovery also drawsattention to the novel effects arising from the inherent large surface-to-volume ratioof nanostructures, which is possibly applicable to many other nanomaterials.