Novel double-hydrophilic block copolymers, maleic anhydride (MA)-allylpolyethoxy carboxylate (APEC) and maleic anhydride (MA) ammonium allylpolyethoxy sulfate (APES), were specially designed and synthesized from allyloxy polyethoxy ether (APEO) to inhibit the precipitation of calcium phosphate and iron (III). Structures of APEO, APEC, MA APEC, APES, and MA APES were characterized by FT-IR. The study shows that both MA APEC and MA APES have significant ability to inhibit the precipitation of calcium phosphate at the dosage of 6 mg/L, approximately showing 99 and 90% inhibition, respectively. The data of the light transmittance of ferrous solutions show that, compared to MA APES, MA APEC has superior ability to stabilize iron (III) in solutions. The light transmittance of ferrous solutions is about 23% in the presence of MA APEC when the dosage is 6 mg/L, whereas in the presence of MA APES, it is about 31% at a dosage of 12 mg/L. Scanning electron microscopy (SEM) shows that the copolymers influence the morphology of calcium phosphate crystallites. Transmission electron microscopy (TEM) indicates the excellent inhibition results from the formation of core shell structure. Double-hydrophilic block copolymers of MA-APEC and MA-APES have also been proven to be effective inhibitors of calcium phosphate and iron (111) even at elevated solution temperature, pH and Ca2+ and Fe2+ concentration.