NOVELTY - Preparing soy saponin B comprises degreasing soy germ by adding 60-90 vol.% of ethanol, refluxing and extracting for 2-5 hours, filtering and concentrating; adding water to the concentrated solution and sampling the raw material in an adsorption column filled with macroporous resin at 20-30 degrees C at a flow speed of 0.5-3 times the column volume/hour of the sample; removing impurities by washing with water for 1-4 times at 20-30 degrees C; evaporating the eluent to obtain crude soy saponin B; and dissolving the crude product in water at 80 degrees C, cooling at 0-30 degrees C, centrifuging and drying.    USE - The soy saponin B is useful: in health food or medicine; and as foaming agent, emulsifier, stabilizing agent and flavor modifying agent.    ADVANTAGE - The process provides soy saponin B with high purity in an eco-friendly manner.    DETAILED DESCRIPTION - Preparing soy saponin B comprises degreasing soy germ, as raw material by adding 60-90 vol.% of ethanol, where the solid to liquid ratio is 1:20, boiling, refluxing and extracting for 2-5 hours, filtering and concentrating the mixture to 1/3-1/5 of the original volume; adding water to the concentrated solution and sampling the raw material in an adsorption column filled with NKA or D101 macroporous resin at 20-30 degrees C at a flow speed of 0.5-3 times column volume/hour of the sample; removing impurities by washing the column volume with water for 1-4 times at 20-30 degrees C and flow rate of 0.5-3 times the column volume/hour; removing the impurities by washing the volume fraction with 5-40% of ethanol for 1-4 times at 20-30 degrees C and a flow rate of 0.5-3 times the column volume/hour; removing the impurities by washing the volume fraction with 5-90% of ethanol for 1-4 times at 20-30 degrees C and a flow rate of 0.5-3 times the column volume/hour; subjecting the obtained eluent to rotary evaporation to obtain crude soy saponin B; dissolving the obtained crude product in water or 30 vol.% of ethanol as crystallization solvent, in a solid-liquid ratio of 1:10-30, at 80 degrees C, cooling the obtained product at 0-30 degrees C and a rate of 1-7 degrees C/hour, centrifuging and drying to obtain pure soy saponin B; and dissolving the volume fraction in water or 30 vol.% of ethanol as the crystallization solvent, where the ratio of solid to liquid is 1:25-45, at 80 degrees C, cooling at 0-30 degrees C and cooling rate of 1-7 degrees C/hour, centrifuging and drying to obtain highly pure soy saponin B.