This paper reports the spectroscopic characterization of the interaction between polyribonucleotides and D-mannitol. The oligoribonucleotides-D-mannitol (ORNs-D-M) complexes possess an anti-influenza activity against the influenza A (H1N1), avian influenza, and parainfluenza viruses. In our assumption, D-mannitol can form a double helix with polynucleotides, like DNA, which explain his antiviral activity. Using different spectroscopic methods, we demonstrate experimental results of interaction between polynucleotides and D-mannitol. We can suppose that mechanism of such interaction is going through nitrogenous base by hydrogen bonds between OH groups in the D-mannitol molecule and oxygen atom or nitrogen atom, in nitrogenous bases.