The present invention provides a method of separating and preparing corosolic acid from loquat leaves, which includes the separation and preparation of the total triterpene acid loquat leaf, the purification of the resin concentration of the corosolic acid, the crystallization and purification of the corosolic acid, etc. In the preparation method, the loquat leaves are used as a material, and the total triterpene acid loquat leaf is extracted by applying the aqueous solution of the hydrophilic organic solvent; under the alkaline condition and before cooling, impurities are removed by filtration, and activated carbon is decolored; extracting solution applies macroporous absorptive resin concentration to purify the corosolic acid, and the crude corosolic acid is further crystallized and recrystallized by applying the hydrophilic organic solvent, so that the high-purity corosolic acid crystal is prepared. By measurement, the purity of the white corosolic acid crystal is larger than or equal to ninety eight percent. The preparation technique of the present invention has the advantages of simple technique, high efficiency of separation and purification, easy industrialized production, high purity of the prepared corosolic acid and low production cost, and moreover, the preparation technique of the present invention has the advantages of high efficiency, high availability, long effect, little dosage, little toxicity, little side effect, convenient storage, convenient carrying and convenient administration, etc. of the modern Chinese medicine.