NOVELTY - L-DOPA (3,4-dihydroxyphenylalanine) is prepared by adding concentrated extract in an extraction device, adding ethyl alcohol 100-200 times than the weight of the raw material Stizolobium cochinchinensis seed, adding inorganic salt, stirring, staying for 0.5-1.5 hours to form two phases, obtaining an upper phase extracting solution, adding water-insoluble and water-soluble two-phase extractant to extract, separating the extracting solution, and adding a water-soluble extractant in the lower solution to extract to obtain a water-soluble extracting solution.    USE - Method for the preparation of Stizolobium cochinchinensis seed L-dopa (claimed) useful in medicine.    ADVANTAGE - The method reduces techniques and has no pollutant emission, obtains L-dopa product with high yield, high purity, less solvent consumption, and low cost.    DETAILED DESCRIPTION - Preparation of S. cochinchinensis seed L-dopa comprises: (A) removing impurities and breaking the raw material S. cochinchinensis seed; (B) adding the pre-treated S. cochinchinensis seed in an extraction device, adding water in a ratio of material to water of 1:3, adjusting the pH value to be 4, lixiviating for 5-10 hours and for 3 times, and combining the extracting solution; (C) introducing the extracting solution in a concentration device to perform a reduced pressure concentration, controlling the temperature not greater than 60 degrees C, and controlling the vacuum degree to be not less than 0. 08 MPa, and concentrating to an extract with 7.5-8.5 Baume degrees; (D) adding the concentrated extract in an extraction device, adding ethyl alcohol 100-200 times than the weight of the raw material S. cochinchinensis seed, and adding inorganic salt, stirring, staying for 0.5-1.5 hours to form two phases, obtaining an upper phase extracting solution, adding water-insoluble and water-soluble two-phase extractant to extract, separating the extracting solution, and adding a water-soluble extractant in the lower solution to extract to obtain a water-soluble extracting solution; (E) de-coloring the extracting solution by active carbon and filtering to obtain a purified extracting solution; (F) crystallizing the purified extracting solution to obtain crystallized L-dopa, distilling the filtrate and recovering the organic solvent; and (G) vacuum-drying, controlling the temperature to be 60 degrees C, controlling the vacuum degree to be 0.08 MPa, and then obtaining the high-purity L-dopa product.