The invention provides an amido-containing ionic liquid used for absorbing acidic gases and a preparation method and application thereof and in particular relates to a method for absorbing acidic gases of CO2, H2S, SO2 and the like by using an amido-containing ionic liquid. The amido-containing ionic liquid comprises one or more of primary amine, secondary amine and tertiary amine, wherein positive ions of the ionic liquid are derived from organic polyamines, negative ions of the ionic liquid are derived from inorganic acid or organic acid, and the ionic liquid is prepared by mixing the organic polyamines with the inorganic acid or organic acid and then carrying out neutralization reaction through acid and alkali. The ionic liquid has the advantages of low cost, simple preparation method,strong absorbing capability and short balance time, can be used for the enriching of acidic gases, the deacidification refining of acid-containing gases of natural gas, refinery gas, methane, coal gas, synthesis gas, coke-oven gas, pyrolysis gas, smoke, motor vehicle tail gas and the like and the purification of gases under a proper space and an operating environment; meanwhile, the ionic liquid absorbing the acidic gases can release the acidic gases through pressure reduction and temperature raise, thus the absorbing capability of the ionic liquid is restored and the multiple absorption property of the ionic liquid is better.