In this paper, polyurethane and its emulsion, with appropriate additives added, are used as binder to replace the traditional resin binder in the experiment of making water-based ink. And then the main mechanism of each component is analyzed. It is indicated that the emulsion makes the binder soak through the paint faster and infiltrate into the particles pores of pigments aggregates by reducing the tension on the surface of monomer and water. Thickener can enhance the viscosity of ink and promote the well-proportioned dispersion of pigment mainly by making the water-based ink form a network on the structure. The surface-active molecules, forming "a protective shell" on the surface of paint, effectively strengthen the affinity between the binder and pigment to make them be fully reconciled and ultimately improve the performance of water-based ink.