Several experiments were desighned to reveeal the reaction mechanism of phenolphthalein during its condensating with DCDPS in presence of potassium carbonate. The results show that the special stereo-structure derived from phenolphthalein's cardo group and its phenol rings makes it possible to form an intermediate complex between the solid potassium carbonate and phenolphthalein

which was proved to benifie to the solvation of solid potassium carbonate

the formation of the phenoxide

and to the further nucleophilic substitution reaction. It is also confirmed that the phenoxides'structures formed in potassium carbonate system are different from that formed inpotassium hydroxide system.Based on our series experimental results

a new reaction mechnism was proposed.