Designing the electron-rich palladium active site is of great importance to enhance the selectivity of ethylene in acetylene semi-hydrogenation. In this work, ionic liquids, the effective electronic modifier, were mingled with palladium solution to be immobilized on Al2O3 by incipient impregnation method. X-ray photoelectron spectra characterization was conducted to characterize the structure of catalysts, suggesting that some ionic liquids can form unique carbene structure. The catalytic results showed that those immobilized ionic liquids that can form unique carbene structure exhibited much higher selectivity of ethylene than those cannot. The above results were obtained because carbene can donor the electron to palladium, enriching the electron density of palladium and therefore facilitating the desorption of ethylene. The findings of the unique carbene structure derived from ionic liquids in this work provide an efficient strategy to design the catalyst to improve the selectivity of the intermediate in other partial hydrogenationreactions.