The invention relates to a metamaterial nano-sensing system, and in particular to a high-sensitivity metamaterial nano-sensing system with an ultra-narrow line width spectral response. The system includes an input light path, a metamaterial nano-sensing unit and an output light path which are sequentially provided along a direction of a light path, and the metamaterial nano-sensing unit includes a Bragg grating and a metallic periodic array arranged above the Bragg grating. The nano-sensing system provided by the invention has an ultra-narrow line width spectral response, so that sensitivity of a nanosensor is effectively improved, and broad application prospect in the fields of portable biosensing, drug development and detection, environment monitoring and the like is ensured.