We proceeded to check the Raman spectra of Rhodamine B(Rh B) under 10~(-11) mol/L and Rh 6G of 10~(-11) mol/L adsorbed in the silver colloid system on the single molecular level by surface enhanced Raman scatter(SERS).We discover that on the single molecular level the Raman spectra of Rh B are far more sensitive,and carry richer information than that of Rh 6G as detecting reagent.The Raman spectra of RhB are almost two times the sensitivity of that of Rh 6G.