The electromagnetic enhancement mechanisms of surface enhanced Raman scattering (SEES) is examined by using Langmuir-Blodgett films as molecule-metal spacer for the first time. In our experiments SERS from the pyridine is monitored as a function of spacer thickness. The experimental results in silver films/LB films/ pyridine+KCL+H2O systems exhibit that SEES effect is still remained with 5nm and no Raman scattering intensity observed with 16 nm spacer thickness. The experiments support electromagnetic enhancement machanisms.