The technique of corrosion inhibitor treatment is one of the most effective ways for silver antitarnishing in accordance with Chinese conservation principles for ancient artifacts. In this paper, the principles and methods of corrosion electrochemical polarization curve and impedance spectrum are introduced which were used in the corrosion inhibitors screening for silver antitarnishing while orthogonal electrochemical experiment was designed for optimizing the formula of composite corrosion inhibitor, the effects of the components and their concentrations on the corrosion parameters, and the optimized silver anti-tarnishing formula was screened out which was composed with MBI (2-mercaptobenzimidazole), MBO (2-mercaptobenzoxazole) and PMTA (1-phenyl-5-mercapto-tetrazole). Test results showed that MBI concentration had the most obvious influence on silver tarnishing among the corrosion inhibitors of the composite formula in Na2S solution, the best ratio of composite corrosion inhibitors MBO:PMTA:MBI was 1:2:3, and their total concentration was 0.0189 mol/L. The accelerated atmospheric corrosion tests in the sulfur sublimate and the vapor of mercapto-acetic acid proved that anti-tarnishing capability of the silver coupon treated with this composite corrosion inhibitor is improved obviously in different corrosive media. Compared with the measurement results of polarization curves and impedance spectra, it can be concluded that the surface characteristics of silver electrode was charged after treated with corrosion inhibitors, the self-corrosion potential moved towards negative direction, the slope of cathodic polarization curve increased, that indicated corrosion cathodic process (dissolved oxygen diffusion) has been inhibited and reduced the corrosion current. The slope of anodic polarization curve increased obviously that indicated the surface protective film isolated silver from the corrosive media to inhibit its tarnishing. When PMTA, MBO and MBI were mixed to use as composite corrosion inhibitors, the inhibition on cathodic and anodic processes were further enhanced, the effectiveness of silver anti-tarnishing was improved in Na2S and mercaptoacetic acid solution. The electric resistance of silver surface protective film formed with composite was up to 343.5k[Omega]·cm2 and the film capacitance was down to 5.09[micro]F·cm-2, it showed that significant synergistic effect occurred among those constitutions of the composite inhibitors. The ancient silver box excavated from the underground palace of Leifeng tower in Hangzhou, Qing Dynasty silver coins and many other silver artifacts treated with the composite corrosion inhibitors, these ancient silver artifacts surface have been kept clean and bright without appearance of any spot for more than one year so far and the anti-tarnishing capability of the silver antiques is improved obviously.