The invention provides a polarity-adjustable ionic liquid, and a preparation method and application thereof. Especially, the polarity-adjustable ionic liquid is not sensitive to water molecules, the polarity of the system can be adjusted by taking CO2 as a molecular switch, and the ionic liquid is applied to circulate and separate low-polarity organic compounds. The polarity-adjustable ionic liquid is prepared by taking an organic alkali and a fluorine-substituted alcohol as raw materials and performing proton transfer reaction, and the ionic liquid is an ionic liquid before and after absorbing CO2. The polarity-adjustable ionic liquid is low in cost and simple in preparation method. The polarity-adjustable ionic liquid absorbing CO2 is increased in polarity, and is capable of separating out low-polarity organic compounds dissolving in the polarity-adjustable ionic liquid. Then CO2 is released through slightly heating, and low polarity of the polarity-adjustable ionic liquid is recovered. The polarity-adjustable ionic liquid is capable of repeatedly dissolving low-polarity organic compounds from mixtures and reaction systems, then helps to separate out low-polarity organic compounds by utilizing CO2 and is good in repeatability.