In order to improve corrosion resistance of copper and its alloy, the synergistic effects between lanthanum salts and BTA was investigated. The corrosion properties of copper alloys were improved greatly after passivation. The morphologies and structure of coating after treating were identified by X-ray diffraction analysis(XRD) and SEM(electron microscope). The effect of lanthanum salts and BTA on the surface preparation for copper alloys was analyzed by anodic polarization curves and EIS impedance measurements. The result shows that the exterior structures of copper alloys is uniformity and compact. So the corrosion resistance of copper alloys by lanthanum salt and BTA conversion coating is improved greatly.