Polyacrylamide (PAM) is a commonly used flocculant that can significantly enhance dewatering performance by adjusting its ionic type and molecular weight. However, the specific mechanisms by which different PAM types and molecular weights impact the solid-liquid separation process still require in-depth investigation. This study examines the effects of high molecular weight polymers with varying ionic types and molecular weights on the solid-liquid separation performance of flotation clean coal, focusing on the mechanism by which PAM improves flocculation dewatering. By experimentally comparing cationic (CPAM) and anionic (APAM) types, as well as various molecular weight PAMs, on clean coal dewatering, the results reveal that both ionic type and molecular weight of PAM significantly impact the cake resistance, filtrate viscosity, and floc structure. High molecular weight CPAM demonstrated optimal performance in reducing cake resistance and improving dewatering efficiency, while APAM primarily enhanced cake compressibility by promoting bridging between particles. Low molecular weight PAMs, in some conditions, struggled to form effective flocs, thereby reducing dewatering efficiency. Selecting the appropriate PAM ionic type and molecular weight can markedly improve the solid-liquid separation performance of flotation clean coal, providing valuable guidance for industrial dewatering processes.