We demonstrated the surface plasmon grating coupled emission (SPGCE) from photo-excited organic layer covered with metal thin film on the corrugated substrate. Directional emissions corresponded to the resonant condition of surface plasmon modes on the Au/air interface. In our experiments, we used different pitch sizes to control plasmonic band-gap which produced highly directional SPGCE with enhanced intensity. Based on our calculation, SPGCE showed a color change from yellowish green to orange at a certain viewing angle, while the concentration of contacting glucose was increased from 10 to 40%, corresponding to the refractive index change from 1.3484 to 1.3968. This indicated a potential application of low-cost, integrated, and disposable refractive-index sensor.