The invention discloses a method for extracting bioactive ingredients in rhizoma polygoni cuspidati. The method includes the following steps that rhizoma polygoni cuspidati is taken, ground, screened with a 18-22-mesh 
sieve and put into a 
reflux tank; 75-85% ethyl 
alcohol with the weight 6-10 times that of rhizoma polygoni cuspidati is added, and 
reflux is carried out for 2.5-3.5 h at 55-65 DEG C; saturated 
ammonium sulfate is added into 
reflux liquid till precipitate is generated, and filtering is carried out to remove precipitate; ethyl 
alcohol is recycled, and 
alcohol extraction liquid is obtained; concentration is carried out, and 
concentrated extract is obtained; water 
precipitation is carried out, and supernatant liquid is taken; concentration is carried out again, and 
concentrated extract is obtained; alcohol 
dissolution is carried out, and supernatant liquid is taken; the supernatant liquid is subjected to plate 
ultrafiltration with SPES, and precipitate and supernatant liquid are collected; separation and purification of 
rheum emodin are carried out, wherein the purity of 
rheum emodin is 99.8%; the supernatant liquid is adsorbed with 
macroporous resin; separation and purification of polydatin are carried out, wherein the purity of polydatin is 99.5% or above; separation and purification of 
resveratrol are carried out, wherein the purity of 
resveratrol is 99.2% or above. According to the method, adopted equipment is simple, the process is simple and feasible, and industrial production is convenient; an adopted 
solvent is free of toxins or residues and does not cause environmental 
pollution.