The SERS spectra of staphylococcus aureus, proteus, and Escherichia coli was obtained on colloidal Ag nanoparticles prepared by the microwave method with the portable Raman spectrometer. Staphylococcus aureus have obvious Raman vibrating peak at 725, 1 330 and 1 450 cm-1, proteus have obvious Raman vibrating peaks at 650, 725, 950, 1 325 and 1 463 cm-1, while E. coli have obvious Raman vibrating peaks at 650, 950, 1 125, 1 242, 1 320 and 1 457 cm-1. Each peak was assigned preliminarily. Not only the position of Raman vibration peaks but also the intensity of the three bacteria is obviously different, so SERS can be used for identification and distinction of E. coli, staphylococcus aureus and proteus.