The invention provides an aspergillus niger strain for efficiently expressing alpha-transglucosidase. The aspergillus niger strain is preserved with the number of CGMCC No.8469. The mutant strain aspergillus niger Atm61 obtained by using an ultraviolet mutagenesis method can be used for realizing the efficient recombination expression of the alpha-transglucosidase, and the activity of a fermenting enzyme is up to 14952U/mL which is increased by 58% than that of a starting strain. The alpha-transglucosidase expressed by the mutant strain aspergillus niger Atm61 can be widely applied to the production of isomaltooligosaccharide syrup and used for increasing the nucleoside transformation efficiency by over 40-50%, and the massic volume ratio of isomaltooligosaccharide in the obtained isomaltooligosaccharide syrup is up to 90%, so that the aspergillus niger strain is wide in market prospect.