The global and local activity of benzotrialole (BTA) and 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) are calculated by density function theory. Thermodynamic properties of BTA and DMTD are simulated by molecular dynamics. The corrosion inhibition effect of mixed system inhibitor is studied through corrosion test. The results show that the inhibition efficiency of DMTD is larger than that of BTA. There are several active sites which focus on N and S atoms. So the inhibitors are absorbed on the surface of Cu in the parallel direction. The specific heat capacities of Cu absorbing inhibitor are the same as those without Cu adsorbing inhibitor at room temperature. The specific heat capacities increase with inhibitor increasing. They provide the reference for the selection of the inhibitor. The effect of mixed system inhibitor is better and the best mixed ratio is BTA: DMTD=1:1.