The invention relates to the field of natural drugs, in particular to a method for extracting and separating a triterpenoid saponin monomer named clematichinenoside AR from a Chinese medicine of radix clematidis. The method is characterized by comprising the following steps of: firstly, extracting the clematichinenoside AR by using an organic solvent and by heating and refluxing; concentrating the extract under reduced pressure to a volume which is 1/10 to 6/10 of the total volume; placing the concentrated solution at a low temperature and subjecting the concentrated solution to high-speed centrifugation and filtration; settling a product obtained from the centrifugation and filtration and evaporating the product to dryness; and obtaining the clematichinenoside AR. The preparation method for the invention is simple and applicable to large-scale industrial production. The product content reaches 85 to 99 percent, and the yield is more than 20 percent.