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.