A method for preparing rubusoside, comprising the steps: providing a dry sample of Sweet tea leaves, crushing and passing them through 40-60 mesh sieve, putting the obtained powder material into a flash extractor, in which water at the amount of 18-20 times by weight of the powder is added, extracting for 3 times, 1 minute for each time, and combining all extract solutions to get the total extract solution; concentrating the total extract solution to a concentrate solution 5 times by weight of the raw leaves, centrifuging the concentrate solution through a disc centrifuge and a tube centrifuge to obtain a centrifugate, and adjusting the centrifugate to pH 5.0-6.0 using an acid solution; passing the adjusted centrifugate through a macroporous resin column, adjusting the effluent to pH 7.0 using 0.2% sodium hydroxide solution, detecting the content of rubusoside and ending sample loading when the content is >1%; when the loading is completed, washing the column firstly using pure water until the effluent is colorless and clear, secondly using alkaline solution until the effluent is PH 11 to 12, thirdly using pure water until the effluent is PH 7.0-7.5, fourthly using an acid solution until the effluent is PH 2.0-2.5, and finally using water until the effluent is PH 7.0; desorbing by 45%-50% ethanol solution, collecting the effluent from the time rubusoside is detected as >1% to the time rubusoside is detected as <1%, and concentrating the effluent under reduced pressure to a concentrate solution of 1035 kg/m 3 (5 Baume); adding a biological enzyme selected from one or a combination of two or more of bromelain, pectinase and neutral protease to the concentrate solution obtained in step, and digesting at a temperature of 45-60 ° C for 1-3 hours to obtain an enzymatic hydrolysate; passing the enzymatic hydrolysate through an organic membrane of 8000 molecular weight under the inlet pressure of 0.45-0.5 MPa, then through an organic membrane of 800 molecular weight under the inlet pressure of 1.8-2.0 MPa to obtain a decolored filtrate; concentrating the filtrate under reduced pressure to obtain a thick paste of 1115 kg/m 3 (15 Baume), adding methanol or ethanol as a solvent at an amount 3 times that of the thick paste, crystallizing at 5-11 ° C for 8-14 hours, drying the obtained crystal to obtain rubusoside. providing a dry sample of Sweet tea leaves, crushing and passing them through 40-60 mesh sieve, putting the obtained powder material into a flash extractor, in which water at the amount of 18-20 times by weight of the powder is added, extracting for 3 times, 1 minute for each time, and combining all extract solutions to get the total extract solution; concentrating the total extract solution to a concentrate solution 5 times by weight of the raw leaves, centrifuging the concentrate solution through a disc centrifuge and a tube centrifuge to obtain a centrifugate, and adjusting the centrifugate to pH 5.0-6.0 using an acid solution; passing the adjusted centrifugate through a macroporous resin column, adjusting the effluent to pH 7.0 using 0.2% sodium hydroxide solution, detecting the content of rubusoside and ending sample loading when the content is >1%; when the loading is completed, washing the column firstly using pure water until the effluent is colorless and clear, secondly using alkaline solution until the effluent is PH 11 to 12, thirdly using pure water until the effluent is PH 7.0-7.5, fourthly using an acid solution until the effluent is PH 2.0-2.5, and finally using water until the effluent is PH 7.0; desorbing by 45%-50% ethanol solution, collecting the effluent from the time rubusoside is detected as >1% to the time rubusoside is detected as <1%, and concentrating the effluent under reduced pressure to a concentrate solution of 1035 kg/m 3 (5 Baume); adding a biological enzyme selected from one or a combination of two or more of bromelain, pectinase and neutral protease to the concentrate solution obtained in step, and digesting at a temperature of 45-60 ° C for 1-3 hours to obtain an enzymatic hydrolysate; passing the enzymatic hydrolysate through an organic membrane of 8000 molecular weight under the inlet pressure of 0.45-0.5 MPa, then through an organic membrane of 800 molecular weight under the inlet pressure of 1.8-2.0 MPa to obtain a decolored filtrate; concentrating the filtrate under reduced pressure to obtain a thick paste of 1115 kg/m 3 (15 Baume), adding methanol or ethanol as a solvent at an amount 3 times that of the thick paste, crystallizing at 5-11 ° C for 8-14 hours, drying the obtained crystal to obtain rubusoside.