Abstract: The mechanisms of caustification and carbonation reactions of lime-flue gas brine purification process were reviwed. Then the CPAM flocculating mechanism of sodium sulfate type brine purification process was discussed：two hydrogen atoms of amide group of CPAM molecules and carbonyl oxygen atoms of the CaCO3 molecules to form a stable quadrilateral hydrogen bond structure，and quadrilateral with CaCO3 molecular internal structure by carbonyl symmetrical structure of the double bonds to form a similar dumbbell，increase the stability of the whole of the molecular structure，and this structure greatly im- proves the flocculating ability of CPAM.Similarly，two hydrogen atoms on molecular amide group of CPAM and two oxygen atoms of sulfuric acid root ion in CaSO4 microcrystalline to form a very stable hexagonal hydrogen bond structure.When the addition of CPAM was 2 mg/L，it′s sure that the calcium′s mass concentration in sodium sulfate type brine was less than 10 mg/L.

Key words: brine purification process, CPAM coagu-flocculation mechanism, quadrilateral hydrogen bond structure, hexagonal hydrogen bond structure