The mechanism of the gelation reaction of chromium (Ⅲ) oligomers with partially hydrolyzed polyacrylamide was investigated with rheological measurements．The oligomers are prepared in relatively pure form using ion exchange liquid chromatography

characterized by UV-visible spectra

oxidation-reduction and exchange liquid chromatography

allowed to react with polymer．When pH value is in the range of 6～12

polymer concentration in the range of 300～1000 and Cr(Ⅲ) concentrations in the range of 2～25 mg/L

the effects of some components on the gelation are investigated．The results show that the advantages of the dimer are low cost and wide pH ranges

suggesting that the formation of Cr oligomer is the rate-determining step in the gelation reaction and the simple binuclear Croligomer is the most reactive species for crosslinking．Thus the detailed mechanism is understood fully．