NOVELTY - Raw materials are crushed, subjected to subcritical water extraction and centrifuged. Ethanol is added to obtained residue (A), centrifuged, and obtained extract is mixed with sodium hydroxide, reacted and filtered to obtain filtrate (A) and betulin. Filtrate (A) is mixed with sodium hydroxide, reacted and filtered. Obtained residue (A) is mixed with ethanol, dissolved in sodium hydroxide, reacted and filtered to obtain filtrate (C) and residue (B). To obtained residue (B), methanol is added, reacted and cooled to obtain betulinic acid precipitated crystals.    USE - Preparation of betulinic acid by subcritical water extraction method (claimed).    ADVANTAGE - The method efficiently and economically provides betulinic acid in short period of time without affecting the environment.    DETAILED DESCRIPTION - Raw materials are crushed to 20-80 mesh to obtain raw material powder. The obtained raw material powder is added to subcritical water extraction apparatus, extracted at 100-200 degrees C in the pressure of 0.5-3.5 MPa for 10-50 minutes, such that the liquid-solid ratio of water and feedstock is 10-50 mL/g, to obtain mixture (A). The obtained mixture (A) is centrifuged at the speed of 3000-5000 rpm for 5-15 minutes to obtain extract and residue (A). Ethanol is added to residue (A) in the liquid-solid ratio of 10-50 mL/g, and stirred at 100-500 rpm for 1-10 minutes to obtain mixture (B). The mixture (B) is centrifuged at the speed of 3000-5000 rpm for 5-15 minutes, to obtain residue (B) and extract (B). The extract (B) is mixed with 5-10% sodium hydroxide, reacted at 1-5 degrees C for 5-10 hours, and filtered to obtain filtrate (A) and betulin. The obtained filtrate (A) is mixed with 5-10 %mass sodium hydroxide, reacted at 1-5 degrees C, maintained for 5-10 hours, and filtered to obtain filtrate (B) and residue (A). The residue (A) is mixed with ethanol in the liquid-to-solid ratio of 10-50 mL/g, dissolved in 5-10 %mass sodium hydroxide, reacted at 30-60 degrees C at 100-500 rpm for 30-90 minutes and filtered to obtain filtrate (C) and residue (B). To the obtained residue (B), methanol is added in the liquid-solid ratio of 10-50 mL/g, and reacted at 30-60 degrees C, and cooled at room temperature, to obtain betulinic acid precipitated crystals.