NaClO was added to the aqueous solution containing nonylphenol. The CHCl3 extract of the chlorination product was analyzed by using GC/MS and LC/MS. Two kinds of products including monochlorononylphenol and dichlorononylphenol were found by both methods.The isomers of nonylphenol and its chlorination products could be detected by GC/MS method.By comparing the relative intensity of the isotope from mass spectrum of the products and the search information from the NIST Library, mono(m/z 254) and dichlorononylphenols (m/z 288) were deduced beside the nonylphenol (m/z 220). In terms of the data from LC/MS, similar results were found. When applying (-) ESI mode, ［M-H］molecular weight for each kind of chlorination compound was obtained.(-)ESIMS direct injection mode could be used as a rapid screening method for analysis of these kinds of compound.