An organic electrolytic solution and a lithium battery employing the same are provided. The organic electrolytic solution includes: a lithium salt; an organic solvent containing a high dielectric constant solvent and a low boiling point solvent; and a carbonate or oxalate derivative having at least one substituted or unsubstituted cyano group. The organic electrolytic solution and the lithium battery employing the same have improved reductive decomposition stability, thereby decreasing an irreversible capacity after a first cycle and improving the charge/discharge efficiency and lifespan of the battery. The lithium battery has non-varying chemical properties at room temperature and a uniform thickness after standard charging, and thus has high reliability.