The invention discloses a simple preparation method for high-purity alpha-cyclodextrin glycosyltransferase. The preparation method comprises the following steps: preparing an alpha-cyclodextrin glycosyltransferase crude enzyme liquid firstly, then enabling fermentation supernatant to sediment by using saturated ammonium sulphate, performing ion exchange column chromatography, performing Native-PAG electrophoretic separation, and finally recovering the electrophoresis of a target protein to obtain the high-purity alpha-cyclodextrin glycosyltransferase. Compared with the prior art, the preparation method has the advantages that the prepared alpha-cyclodextrin glycosyltransferase is high in purity, the preparation steps are few, the production efficiency is high, the requirement of cyclodextrin for industrial production can be met, the difficulty in later purificiation of the cyclodextrin is lowered, the production cost of the cyclodextrin is greatly reduced, the application of CGTase and the mass production of the cyclodextrin are improved to a great extent, and the preparation method ahs popularization and application value.