Abstract: There is currently no research on the dynamic flocculation process of difficult−to−settle coal slurry water. The presence of clay minerals such as kaolin is the main reason for the poor settling effect of coal slurry water. Compared to the toxicity of polyacrylamide (PAM) synthesized monomers, starch−grafted acrylamide (SAM) synthesized monomers have better degradability.Therefore, the effects of SAM and PAM on the dynamic flocculation process of kaolin were systematically compared. Firstly, the sedimentation rate and flocculation performance were investigated under different dosages of SAM and PAM. Subsequently, the changes in the number of different particle sizes of kaolin suspension under the action of SAM and PAM were studied using focused beam reflectance measurement (FBRM) coupled with particle video microscopy (PVM). The settlement and FBRM−PVM results indicate that PAM can form more large flocs of +100 μm, which leads to a better settling effect using PAM. The flocs formed by SAM are more stable, resulting in a better flocculation performance for ultrafine particles. Finally, the flocculation kinetic parameters of kaolin using PAM and SAM were calculated by fitting the data obtained from FBRM to Smoluchowski’s model. It was found that PAM produced a significantly higher flocculation index compared to SAM. Meanwhile, the changes in the number of −30 μm and 30−60 μm particles dominated the formation process of flocs in flocculation kinetics. In conclusion, PAM can form more loose and large flocs, which is beneficial for the rapid settlement of kaolin. However, SAM has a superior flocculation performance of ultrafine particles than that of PAM. Compared to PAM, the unique multi−chain three−dimensional network structure of SAM is conducive to the flocculation of fine particles and the formation of stable flocs, which can avoid the cyclic accumulation of fine mud in the washing water system of coal preparation plants.