CO2 electroreduction reaction (CO2RR) to syngas with a tunable CO/H2 ratio and high current density is a promising but challenging application. Here, we report a novel electrolyte, including protic ionic liquid (IL) [Bim][NTf2], nonprotic IL, acetonitrile (MeCN) for CO2RR to syngas. When the concentration of [Bim][NTf2] increased from 0.005 to 0.12 mol·L-1, the CO/H2 ratio dropped from 30 to 0.1 and the current density increased from 26.4 to 113.4 mA·cm-2 at -2.3 V vs. Ag/Ag+ in H-cell. The [Bim][NTf2] not only can generate H+ to accelerate HER, but also increases the CO2 solubility to promote CO2RR to CO. Meanwhile, the [Bmim][NTf2] mainly increased the current density for CO2RR. By varying the concentration of [Bim][NTf2], the CO/H2 ratio could be modulated in ternary electrolyte. This work offers a novel method to modulate the CO/H2 ratio for enhancing the efficiency of CO2RR to syngas with a high current density in H-cell.