Silver nanoparticles were prepared by chemical method using citricacid trisodiumsalt (Ag-CTS) and polyvinylpyrrolidone (Ag-PVP) as surface modifiers, respectively. When Ag-CTS or Ag-PVP nanoparticles were added into methyl orange (MO) solution, the enhanced-fluorescence of S1→S0 and quenched-fluorescence of S2→S0 were simultaneously observed. However, for the solution containing Ag-PVP, the red-shift of fluorescence peak of S1→S0 was observed and the extents of the enhanced-fluorescence of S1→S0 and quenched-fluorescence of S2→S0 are higher than those of the solution containing Ag-CTS. With the increase in reaction time the fluorescence intensity of S1→S0 increased gradually in the solution containing Ag-CTS nanoparticles and no change was observed in the solution containing Ag-PVP nanoparticles. The lower the MO concentration, the higher the fluorescence intensity ratio of S1→S0. The results indicated that the silver nanoparticles with different surface modifiers affect the metal-enhanced fluorescence by impacting the distance between the methyl orange and silver nanoparticles. The size of silver nanoparticles affects the metal-enhanced fluorescence due to the difference in the surface plasma resonance properties.