4-chloro，4-hydroxydiphenylsulphone was prepared by the hydrolysis of 4，4’-dichlorodiphenylsulphone with sodium hydroxide in the presence of the solvent DMSO．When the molar ratio of DDS/Na0H equal to 1：2.5 the hydrolysis will be eompleted．The contents of 4，4’dihydroxydiphenylsulphone and 4，4’-dichlorodiphenylsulpllone in 4 ehloro，4-hydroxydiphenylsulphone were determined．Then according to analytieal results，4，4’-diehlorodiphenylsulphone was added to the system of the eopolycondensatibn at different molar ratio of (Cl)/(OH) and then copolycondensed respectively．Inthe system，the end．groupsofthethreemonomers (NaO SO2 一Cl (I)，NaO--◇一SO2—ONa (Ⅱ) ana Cl——SO2--Cl (III) exhibit~ifferent reactivities．Reactivity of the sodium phenoxide-end-group is (II)>(I)，while reactivity of the chloride-end．group is (III)>(I)．In the copolycondensation the difference in molar ratio of the three monomers has noticeable effect not only on the initial eopolycondensation rate，but also on the proper-ties of polymer vbtained，and in case of (Cl)/(OH)>1 the polymer obtained will possess best properties．