A series of phenolphthalein containing copolymers were synthesized from nucleophilic polycondensation of 4,4′-dichlorobenzophenone (DCDPK),4,4′-dichlorodiphenyl sulphone (DCDPS) and phenolphthalein (PP)．In order to investigate their chain structures,13C-NMR spectra of these copolymers were recorded．The average sequence lengths,the degrees of randomness and compositions of the copolymers were calculated from the intensities of three kinds of signals,which corresponded to the chemical shifts of three kinds of quaternary carbon atoms in phenolphthalein units in the copolymers．The same results obtained from the three sorts of signals indicated that except the block copolymer,the degree of randomness of other copolymers was approximate to 1,in other words,these copolymers were random copolymers．