2-Methacryloyloxyethyl choline phosphate (MCP) was synthesized by a ring-opening reaction of cyclic phosphates with 2-(dimethylaminoethyl methacrylate). The crude MCP consisted of an endo-cyclic desired product and an exo-cyclic byproduct. The exo-cyclic byproduct was completely removed by anion-exchange and subsequent open-column chromatography. We successfully obtained pure MCP without the exo-cyclic byproduct, and synthesized MCP polymers by free radical polymerization.