Thisresearchreportsthepreparationandcharacterizationofcoppernanoparticlesmodifiedbydidecylbenzenesulfonate(DBS),TheCunanoparticles'sizewasdeterminedtobe40nmbytransmissionelectronmicroscope(TEM).TheX-rayphotoelectronspectrometry(XPS)resultsshowthatthereareinteractionsbetweenthecoppernanoparticlesandDBSfunctiongroup.Thenonlinearopticalpropertieswerestudiedbythefour-wavemixingmethod.Thevalueofx^(3)/α0wasfoundtobe6.9×10^-11esucm.