The present study explored a probe type gas detection system which can be used to detect the gas conveniently. The gas sensing mechanism is utilizing Localized Surface Plasmon Resonance (LSPR) sensor which based on the reflected light change caused by the refractive index changes of gas where exposing to the metal nanoparticles layer. The LSPR layer was prepared by vacuum sputtering of AuNPs on a glass substrate, growing in silver growth solution and consequently thermal annealing. An optical system which composed of fiber probe, light source and spectrometer was developed to detect the change of reflected light. It was found that compared with incident light irradiating from metal nanoparticles side, glass side could obtain clearer spectra peak. In addition, a LSPR sensor which had 5 hours silver growth time has the best response to acetic acid gas. This work demonstrated that the reflection detection system has a great potential in gas detecting area.