Enzymatic modification of steviol glycosides using the glucosyl transfer activity of medium-temperature α-amylase BAN 480L has been investigated in this paper.Experimental results showed that,with potato starch and steviol glycosides as the substrates,transglycosylation reaction occurred mainly on stevioside that in need of improvement of the taste quality,while rebaudioside A,the component with the best quality of taste,was rarely transglycosylated.Under the optimized reaction conditions of steviol glycosides 20 g/L,potato starch 160 g/L,temperature 70 ℃,pH 6.5,enzyme loading 2 KNU/g starch,and reaction time 6 h,the conversion yield of stevioside was 38.9%.The removal of starch sugar and the purification of products were carried out by macroporous resin separation.Evaluation of the organoleptic properties of the product revealed the significant improvement for both the intensity and quality of the taste.