The soluble poly[methyl[4-(phenylthio)phenyl]sulfonium trifluoromethanesulfonate] (PPST) in organic solvents was synthesiszed by self-condensation polymerization of methyl - (phenylthio)phenyl sulfoxide. Sulfonated poly(phenylene sulfide)(SPPS) derivative was prepared by sulfonating PPST with fumic sulfonic acid(10% SO3-H2SO4) and demethylation with aqueous NaOH solution. The optium conditons of the sulfonation of PPS which was obtained by ion exchange capacity and IR absorbance were reaction time 12hr, reaction temperature 150 ℃. Ion exchange capacities of SPPS, which was obtained by IR absorbance, was 11.5meq/g and the degree of sulfonation per repeat unit was 2.19. The sulfonation reaction above 150 ℃ resulted in a decrease in the degree of sulfonation because the crosslinking reaction took place through dehydration between the sulfonic acid and near phenyl groups. As PPs was sulonated, glass temperature(Tg) increased and initial degradation temperature decreased.