Abstract: Nano-grating is a novel subwavelength artificial surface with spatial modulation function for both phase and amplitude of the incident light. The incident light can be reflected, transmitted or resonated from the artificial surface. A highly reflective nano-grating structure was designed, and its inherent physical mechanism of high reflection was analyzed. The results show that the nano-grating has two main propagation modes. And due to the interaction between the two modes, nano-grating demonstrates high reflection, high transmission, high-Q resonance and other physical phenomena.