Carbon monoxide generation reaction of vinylene carbonate (VC) in the electrolyte solution of lithium ion batteries (ethylene carbonate (EC) and 1.0 M LiClO4/EC) is studied using the RISM-SCF-SEDD method, a hybrid methodology of statistical mechanics for molecular liquids and quantum chemistry. The analytical treatment of the solvent and lithium salt enables us to treat the complicated composition of the solution such as the concentration of the salt which is difficult for the methods based on the molecular dynamics (MD) simulation. The free energy profile and solvation structure are discussed in order to clarify the effect of the solvent, especially lithium salt on the reaction. The lithium salt strongly stabilizes the system due to the electrostatic interaction compared with the system in which the salt does not exist:The effect of the salt is especially important for considering the ionization process VC.