Co-polypeptides containing 3,4-dihydroxyphenylalanine (DOPA) and L-lysine were synthesized to mimic the marine adhesive proteins through ring-opening polymerizations. The effects of composition, molecular weight, and curing agents on the adhesive properties, swelling, and degradation behavior of synthetic polypeptide were investigated. Ferric ion was introduced to the system to optimize both adhesive strength and water resistance, simulating the specificity of metal-mediated cross-linking of the marine mussel adhesives. The polypeptide was used to bond on porcine skin and porcine bone in vitro to evaluate the adhesive properties. Furthermore, outcomes of the cell culture of both co-polypeptide and co-polypeptide-modified ethylene vinyl acetate (EVA) demonstrated good cell affinity, which would provide basic data for the application of the co-polypeptide in the biomaterial field.