The synergistic corrosion inhibition performance of 3, 3'-Diethylthiadicarbocyanine iodide (DI) and Thioflavin T (TT) for copper in 0.1M HCl solution was investigated by electrochemical methods, weight loss tests and SEM. Besides, through the thermodynamics and kinetics analysis, the effects of temperature and concentration were explored. The XPS was also applied to study synergistic inhibition mechanism between anions and cations of ionic liquid. The results indicated that the inhibitor molecules interacted with copper forming protective film to inhibit corrosion by physical and chemical adsorption, also the organic cations and halogen ions had synergistic corrosion inhibition. With theoretical calculation and molecular dynamics simulation, the experiment validity was further assessed.