A process for producing a highly purified glucosyl stevia composition, comprising the steps of: adding starch into water to form a starch suspension; adding a mixture of α -amylase and CGTase into the starch suspension and incubating for about 0.5 to 2 hours at about 75-80°C, resulting in a liquefied starch suspension; inactivating the α -amylase by low pH heat treatment; cooling the liquefied starch suspension and adjusting the pH to about 5.5 to 7.0; adding steviol glycosides into the liquefied starch suspension, resulting in a reaction mixture; adding a second batch of CGTase into the reaction mixture and incubating for about 12 to 48 hours at about 55-75°C; adding β -amylase to the reaction mixture and incubating for about 12-24 hours at about 35-55°C; inactivating the enzymes in the reaction mixture by heat treatment; decolorizing the reaction mixture; removing non-diterpene compounds by contacting the decolorized reaction mixture with macroporous adsorbent resin and subsequently eluting adsorbed diterpene glycosides with aqueous ethanol to result in a glycoside-containing aqueous ethanol eluate; desalting the glycoside-containing aqueous ethanol eluate with ion-exchange resins; removing ethanol from the aqueous ethanol eluate, resulting in an aqueous eluate; concentrating and drying the aqueous eluate to obtain the dried glucosyl stevia composition, suspending the dried glucosyl stevia composition in aqueous alcohol to form a suspension, removing unmodified steviol glycosides from the suspension, and separating and drying the highly purified glucosyl stevia composition; wherein the highly purified glucosyl stevia composition comprises short-chain steviol glycoside derivatives having two or less α -1,4-glucosyl residues, and less than about 15% unmodified steviol glycosides. adding starch into water to form a starch suspension; adding a mixture of α -amylase and CGTase into the starch suspension and incubating for about 0.5 to 2 hours at about 75-80°C, resulting in a liquefied starch suspension; inactivating the α -amylase by low pH heat treatment; cooling the liquefied starch suspension and adjusting the pH to about 5.5 to 7.0; adding steviol glycosides into the liquefied starch suspension, resulting in a reaction mixture; adding a second batch of CGTase into the reaction mixture and incubating for about 12 to 48 hours at about 55-75°C; adding β -amylase to the reaction mixture and incubating for about 12-24 hours at about 35-55°C; inactivating the enzymes in the reaction mixture by heat treatment; decolorizing the reaction mixture; removing non-diterpene compounds by contacting the decolorized reaction mixture with macroporous adsorbent resin and subsequently eluting adsorbed diterpene glycosides with aqueous ethanol to result in a glycoside-containing aqueous ethanol eluate; desalting the glycoside-containing aqueous ethanol eluate with ion-exchange resins; removing ethanol from the aqueous ethanol eluate, resulting in an aqueous eluate; concentrating and drying the aqueous eluate to obtain the dried glucosyl stevia composition, suspending the dried glucosyl stevia composition in aqueous alcohol to form a suspension, removing unmodified steviol glycosides from the suspension, and separating and drying the highly purified glucosyl stevia composition; wherein the highly purified glucosyl stevia composition comprises short-chain steviol glycoside derivatives having two or less α -1,4-glucosyl residues, and less than about 15% unmodified steviol glycosides.