The principle of surface plasmon resonance phenomenon and excitation condition of SPR are described in the paper .The relationship between the resonant angle produced by the prism SPW sensor and liquid refractive index as well as dielectric constant is analysed based on the electromagnetic field theory and particle vibration. The SPR depends on the permittivities both the metal and the dielectric medium,and its energy is localized at the interface. So this kind of senor has high sensitivity to changes in the refractive index and configuration of the surface. Surface plasmons are excited at a specific incident angle and result in a massive reduction in reflectivity at that angle required for excitation. Changing in the interfacial refractive index results in a change of the optimal angle required for excitation .Using a prism SPW sensor testing system ,measure the relationship between different concentration from 0% to 70% glycerine solution refractive index and resonant angle. Experimental results obtained ha