A sensing system comprises a light source, an optical fiber, a plurality of noble metal nano-particles, a micro-fluidic module and a photo detector. The optical fiber couples an incident light. The plurality of noble metal nano-particles are disposed on a surface of the optical fiber to form a noble metal nano-particle submonolayer, the noble metal nano-particles are substantially separated from each adjacent noble metal nano-particles such that the conductivity of the noble metal nano-particle submonolayer is smaller than that of a metal film. The micro-fluidic module accommodates the optical fiber and a sample, and the sample is driven to contact with the noble metal nano-particles. The photo detector detects an emergent light from the optical fiber. When the incident light interacts with the noble metal nano-particles, a signal derived from localized surface plasmon resonance in form of attenuated light or elastic scattered light is outputted through the photo detector.