A method for the preparation of pharmaceutically acceptable chlorogenic acid, that includes the following steps: a. Preparing sample aqueous solution: the sample is dissolved in purified water to prepare the solution of chlorogenic acid at a concentration ranging from 20 mg/ml to 2000 mg/ml, and filtered; in which the sample is extracted from leaves of Eucommia ulmoides and then isolated to have a chlorogenic acid concentration of no less than 60%; the preparation temperature is up to 60 °C; b. Freezing: the filtrate is frozen at a temperature of below 0 °C until it fully becomes ice; c. Thawing and filtering: the ice obtained by freezing is thawed under the conditions of 5∼60 °C temperature, and the temperature of thawing solution is up to 5 °C, then the solution is filtered; d. Treating the residue organic phase: the residue obtained by filtration is dissolved in organic solvent, then filtered, to provide the organic solution; in which the organic solvent is selected from any one of methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; the dissolving temperature is up to 60 °C; e. Concentrating and crystallizing: the organic solution is concentrated under the conditions of low temperature and negative pressure, until the precipitation forms, then the solution is allowed to stand for crystallizing; the concentration temperature is up to 60 °C, and the vacuum degree is 0.04 Mp or above; f. Choosing the number of times to repeat steps a∼e according to the variability of chlorogenic acid content in samples; when the content in the extract is 60-80%, steps a-e are repeated twice; when the content in the extract is 80-90%, steps a-e are repeated once; when the content in the extract is more than 90%, it is not necessary to repeat steps a-e; g. Drying: after the crystals are filtered out, they are dried at low temperature; the dry temperature is up to 60 °C, and drying is performed under normal or negative pressure. a. Preparing sample aqueous solution: the sample is dissolved in purified water to prepare the solution of chlorogenic acid at a concentration ranging from 20 mg/ml to 2000 mg/ml, and filtered; in which the sample is extracted from leaves of Eucommia ulmoides and then isolated to have a chlorogenic acid concentration of no less than 60%; the preparation temperature is up to 60 °C; b. Freezing: the filtrate is frozen at a temperature of below 0 °C until it fully becomes ice; c. Thawing and filtering: the ice obtained by freezing is thawed under the conditions of 5∼60 °C temperature, and the temperature of thawing solution is up to 5 °C, then the solution is filtered; d. Treating the residue organic phase: the residue obtained by filtration is dissolved in organic solvent, then filtered, to provide the organic solution; in which the organic solvent is selected from any one of methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; the dissolving temperature is up to 60 °C; e. Concentrating and crystallizing: the organic solution is concentrated under the conditions of low temperature and negative pressure, until the precipitation forms, then the solution is allowed to stand for crystallizing; the concentration temperature is up to 60 °C, and the vacuum degree is 0.04 Mp or above; f. Choosing the number of times to repeat steps a∼e according to the variability of chlorogenic acid content in samples; when the content in the extract is 60-80%, steps a-e are repeated twice; when the content in the extract is 80-90%, steps a-e are repeated once; when the content in the extract is more than 90%, it is not necessary to repeat steps a-e; g. Drying: after the crystals are filtered out, they are dried at low temperature; the dry temperature is up to 60 °C, and drying is performed under normal or negative pressure.