Dimethoate coating was obtained by evaporating staturated dimethoate solution on Ag film which was prepared by magnetron sputtering.Vibrational Spectra of dimethoate coating was studied by surface-enhanced Raman scattering(SERS).The results showed that the failure of crystal structure makes the widening and blue shift of υ(P—S) and υ(P‖S) modes in dimethoate coating SERS system,hydrolysis causes the intensities of δ(SPOC) and δs(COPOC) decreasing,the adsorption of O,N(O‖C—N) and the protonated O on Ag film induces the increase of υ(O‖C—N),υ(O‖C),δ(N—H),υ(CN),δ(C—N—C),δ(OPO) and υ(P—O) modes.The results could be used in the studies of dimethoate solution,and its residues in plants and food samples.