Different molecular weights of polyacrylic acids were prepared through change the molar ratio of acrylic acid (monomer), sodium bisulfate (chain transfer agent) and potassium sulfate (initiator). Using polyacrylic acid as the intercalation agent, the intercalation method was applied to Suzhoutu modification. The paper researched the affections of intercalation agent’s molecular weight on fluidity, thixotropy, absorption rate and plasticity of pulp. The changes in the interplanar spacing of clay were detected by X-ray diffraction analysis. Results showed that appropriate molecular weight of the polymer intercalation agent has little effect on the interlayer structure of Kaolinite, while the effect is obvious to Illite, and processability of the clay was significantly improved.