In this paper, we propose a newly designed dispersant, ammonium poly(methacrylate)-block-poly(2-phenoxyethyl acrylate) (PMA-b-PBEA), and our rheological and zeta potential test results verify its superior dispersion efficiency for aqueous suspensions in comparison to the commercial dispersant ammonium polyacrylate (PAA-NH4). The extremely high dispersion efficiency of PMA-b-PBEA correlates closely to its diblock structure, which simultaneously exhibits a less polar anchoring head group and a water-dissociable stabilizing moiety. The unique structure of PMA-b-PBEA accounts for its high powder adsorption effectiveness, which is demonstrated in its adsorption capability being double that of PAA-NH4.