The invention provides a method for preparing disodium 5'-ribonucleotide, which comprises the following steps of: preparing phosphoryl dihalide (II), reacting nucleoside with the phosphoryl dihalide (II) to obtain nucleoside phosphodiester (III), and performing R-radical substitution and salifying on the nucleoside phosphodiester (III) to obtain the disodium 5'-ribonucleotide (I). The method has the advantages of high conversion rate, a few byproducts, easy purification, easier impurity removal, reduction in postprocessing difficulty, and capability of preparing the disodium 5'-ribonucleotide with high purity and yield.