A new soap-free water-borne coating (solid content ca. 35 wt %) has been obtained by adding the coordination-crosslinking agent M(NH3)(4)(2+) into the -COO--containing polyacrylate hydrosol (P-COO-). The transmission electron microscope analysis has been used to investigate the coordination-crosslinking process of the polyacrylate hydrosol with Zn(NH3)(4)(2+) in the water-borne coating of low concentration (solid content 0.05 wt %). The existence of the coordination-crosslinking polymer (P-COO-)(n)M2+ both in the water-borne coating of low concentration (solid content ca. 0.3 wt %) and in the coating film has been detected hy the linear sweep voltammetry polarographic analysis, ultraviolet-visible spectrographic analysis, and IR spectrographic analysis. All the experimental results show that the polyacrylate hydrosol (P-COO-) can take the coordination-crosslinking reaction with metal ion M2+ to form the coordination polymer [(P-COO-)(n)M2+].