It has been proved that Ga can substitute for Fe in many biologic systems and inhibit Fe-dependent processes because its chemical structure is similar to that of Fe. Herein, the titanium chip was coated with a thin layer of gallium nitrate successfully, and the inhibitory effect of Ga on P. aeruginosa and S. aureus biofilms formation was studied in details. It was found that the gallium nitrate coating was very effective to prevent P. aeruginosa from forming biofilms, but was almost invalid for S. aureus. The minimum inhibitory concentration of Ga was tested, and the results showed that the inhibitory effect of Ga against P. aeruginosa became significant when the concentration was over 40 mu M. It was also demonstrated that Ga dramatically inhibited the growth and auto-aggregation of P. aeruginosa. Furthermore, the crystal violet staining method revealed that the gallium nitrate coating could resist P. aeruginosa from reproducing effectively. The chips were then incubated at 37 degrees C to test the antimicrobial durability, and it was found that the antimicrobial activity was still obviously even after being incubated for more than 25 days. So this novel coating is likely to improve the treatment effects of implanted biomaterials.