Abstract: Formaldehyde aqueous solutions of three different initial concentrations (25, 500, 11 000 mg/L) were degraded by direct irradiation via electron accelerator (maximum beam power 0.8 kW). The radiolysis of formaldehyde aqueous solution was analyzed via ultraviolet (UV) absorption spectrum and liquid chromatography (LC). It is obtained that the residual mass fraction of formaldehyde solution decreases exponentially with the increase of absorbed dose. At least 4 major radiolysis products, which include formic acid and one kind of oligomer, are discovered. And it is also found that the radiolysis efficiency can increase doubly with an addition of NaOH. Accordingly, electron beam radiation could be an efficient process for degradation of formaldehyde aqueous solution with various concentrations.