||Cation exchange membranes are used in related industries such as capacitive deionization (CDI), electrodialysis, fuel cells. In order to improve the mechanical properties and chemical durability of poly(2,6-dimethylphenylene oxide)(PPO) cation exchange membranes which can be used for CDI water treatment, they were crosslinked. BADGE, resorcinol diglycidyl ether, tris(2,3-epoxypropyl) isocyanurate and tris(4-hydroxyphenyl)methane triglycidyl ether were used as crosslinking agent. The properties such as ion exchange capacity, electrical resistance, water uptake of PPO cation exchange membrane were measured and analyzed according to contents of crosslinking agents. In addition, solubility in organic solvents and CDI performance before and after crosslinking were investigated. The mechanical properties and the chemical durability of used membranes could be improved without sacrificing the electrochemical properties of membrane within a certain degree of crosslinking.