Molecular fluorescence spectra of dye adsorbed on silver colliod and silver mirror were studied. Acriding Orange was used as sample in the experiment. We have found that the enhancement or quenching are depend on the competition of two processes, i.e., local field enhancement and non-radiation energy transfer from the molecule to metal surface. The fluorescence is enhanced when enhanced absorption and enhanced emission conditions are achieved. However, molecular fluorescence is far less enhanced then Raman. Theoretical calculation shows that peak enhencement of fluorescence intensity will be 10-102. It agrees with the experimental value for Acriding Orenge adsorbed on silver mirror.