As dispersants of coal water slurry (CWS), two kinds of amphiphilic copolymers were synthesized by grafting of poly(styrene-co-maleic anhydride) with 1-naphthylamine-6-sulfonic acid alone (SMANS) or together with methoxypolyethlene glycol (SMANP), and characterized by H-1 NMR and GPC. Their effects on the rheological behaviors and stability of MS were investigated. The Cross model was employed to quantitatively describe the rheological behavior of CWS. It was found that amphiphilic copolymer dispersants remarkably reduced the viscosity and improved the stabilization of CWS. The electrostatic repulsion and steric hindrance generated by the copolymer dispersants are believed to play an important role. With the presence of sulfonate groups, both kinds of copolymer dispersants can provide electrostatic repulsion among coal particles after adsorption. For SMANP, the polyethlene glycol (PEG) pendants offer additional steric hindrance to further stabilize the CWS. On the basis of these results, the mechanism of dispersion and stabilization of CWS by the copolymer dispersants was proposed.