NOVELTY - Extracting and separating 24-dehydrocholesterol and cholesterol using ionic liquid, comprises: (a) dissolving a mixture of 24-dehydrocholesterol and cholesterol in a raw material solvent to obtain a raw material solution, adopting an ionic liquid or a binary mixed solvent of the ionic liquid and a polar solvent as extracting agent, and carrying out multistage countercurrent contact; and (b) vacuum concentrating the extracted residual liquid, washing and drying to obtain cholesterol, re-extracting the extracted liquid, vacuum concentrating, washing and drying to obtain 24-dehydrocholesterol.    USE - The method is useful for extracting and separating 24-dehydrocholesterol and cholesterol using ionic liquid.    ADVANTAGE - The method adopts the ionic liquid as the extracting agent, which has thermal stability, high selectivity and non-flammable properties in comparison with the traditional solvents; and is simple, safe, environmental friendly and suitable for industrial production.    DETAILED DESCRIPTION - Extracting and separating 24-dehydrocholesterol and cholesterol using ionic liquid, comprises: (a) adopting a mixture of 24-dehydrocholesterol and cholesterol as a raw material, dissolving in a raw material solvent to obtain a raw material solution, adopting an ionic liquid or a binary mixed solvent of the ionic liquid and a polar solvent as an extracting agent, where the raw material solvent is detergent, and fractioning and extracting; where the fractioning and extracting process is divided into an extracting section and a washing section, the extracting agent from the first level of the extracting section is conveyed to the extracting system, the raw material solution from the last level of the extracting section is conveyed to the extracting system, the washing agent from the first level of the washing section is conveyed to the extracting system and then combined with the material solution in the last level of the extracting section and conveyed to the extracting section, and carrying out multistage countercurrent contact of the extracting phase and the washing phase, where the extracted residual liquid enriched with cholesterol flows out from the first level of the extracting section, and the extracted liquid enriched with the 24-dehydrocholesterol flows out from the first level of the washing section; and (b) vacuum concentrating the extracted residual liquid in the step (a), washing with water and drying to obtain cholesterol; re-extracting the extracted liquid in the step (a) with n-hexane, vacuum concentrating the n-hexane extraction phase, washing with water and drying to obtain 24-dehydrocholesterol; where the ionic liquid is composed of cation M+ and the anion L-, where the cation M+ is imidazolium cation, pyridinium cation, quinolinium cation, isoquinolinium cation or benzimidazolium cation (all optionally substituted by alkyl, alkenyl, phenyl, cyano, thiocyano, sulfone or carbonyl).