The invention discloses a method for purifying stevioside RD (Rebaudioside D), which comprises the steps of: preparing mother liquor stevioside into 25-40mg / ml of feed liquid, enabling the feed liquid to flow through a macroporous adsorption resin column at a speed of 2.5-4.0L / min, wherein the resin column is a styrene polar copolymer, the average pore size of the resin column is 40-50A, the pore capacity is 0.9-1.0ml / g, the pH value during the adsorption is 4.5-5.5; and after the complete absorption, eluting and adsorbing on the stevioside absorbed on the resin column with alcohol with mass concentration of 75-80 percent, collecting eluent by sections, determining a critical point, collecting eluent at the critical point, concentrating the eluent at a temperature of 60-80 DEG C, and respectively drying obtained solid and liquid to obtain coarse stevioside. The stevioside obtained by using the method has higher purity, and the content of the RD can reach above 40 percent; and the content of the RD in the stevioside can reach above 95 percent through a refining step.