In our pervious investigation,we found that the synthetic process of PPS was dominated by a condensation which,in turn,was followed by a selfpolycondensation of AB type.In the first place,the solvent action of Na+ was inccured by the two solvent(NMP and HMPA) Na2S+2xNMP=2Na(NMP)+x+S2-......(1) Therfore,the S= was fully bared and it is nueleophilic reactivity was raised.The reaction of the high active bare S= and pdichlorobenzene was carried out easily ClC6H4Cl+S2-=ClC6H4S-Cl-............(2) The productive pchlorothiophenol anion was followed by a selfcondesation nClC6H4S-=Cl-n+(n-1)Cl-......(3) Thus an apparent kinetices expression of the polycondensation was found as 1(1-PNaCl+PNa2S)=c0·k·t+1(4) And,the equilibrium constant of synthesizing PPS was expressed as follows K1K2K3=2·2.........(5) In which K1,K2,K3 are equilibrium constants of the chemical reactions(1),(2),and(3),respectively.