The invention belongs to the technical field of biochemical engineering, relates to an improved method for producing 5'-flavor nucleotide and particularly relates to a method for constructing a gene engineering bacterium through a DNA (deoxyribonucleic acid) recombination technology, carrying out mutant screening on the gene engineering bacterium and utilizing the high-activity gene engineering bacterium to produce 5'-nucleotide. The method comprises the following steps: 1, through the DNA recombination technology, constructing an acid phosphatase expression vector, and converting into Escherichia coli to obtain a gene engineering bacterium capable of efficiently expressing acid phosphatase; 2, mutating the gene of the acid phosphatase, and screening the acid phosphatase having high affinity with nucleoside; and 3, using the acid phosphatase to catalyze the nucleoside and a phosphate group donor so as to synthesize the 5'-nucleotide. By using the method to realize the catalytic synthesis of the 5'-nucleotide, the invention has the characteristics of simple process, high efficiency, short period, less bacterium consumption, low cost and the like, conforms to environment protection requirements, and is suitable for industrial production.