In this paper, the low grade Ca-bentonite from Liaoning was taken as the object of the study and the wet processing technology of purification was employed. The influence of such factors as the tape and dosage of dispersants, the liquid-solid ratio, the speed of centrifugation, the time of centrifugation and the temperature of bentonite on the content of bentonite was determined. The characterization of original soil and the purity of bentonite were tested by the X-ray diffraction photographs. The experiments show that the best conditions for purification are as follows: the concentration of dispersant is 0.5%, the liquid-solid ratio is 12, the time of centrifugation is 9 min, the speed of centrifugation is 2 500 r/min, and the temperature of bentonite is 60℃. The purity of montmorillonite can be raised up to over 92% after purification.