The substitutions of the chlorine atoms in p-dichlorobenzene (DCB) or the chlorine end-groups of polyphenylene sulfide (PPS) by sodium N-methyl-4-aminobutyrate (SMAB) are important reactions in the polymerization of PPS. The reaction process of DCB with SMAB was studied under conditions similar to the polymerization of PPS. The molecular structures of the products were analyzed through high-performance liquid chromatography, liquid chromatography-mass spectroscopy, gas chromatography-mass spectrometry, and other methods. Several pairs of para- and meta-isomer products were found, which indicates the coexistence of both nucleophilic addition–elimination (SN2Ar) mechanism and aryne intermediate mechanism. Based on mechanism analysis, the networks of reactions of DCB with SMAB were proposed and the effects of the ratio of SMAB to DCB, water content, and temperature on the reaction process were studied.