Low flow-resistant methacrylate-based C18 monolithic stationary phases were fabricated for capillary ion chromatography by thermally initiated radical polymerization of octadecyl methacrylate(ODMA) and ethylene glycol dimethacrylate(EDMA) in a 530μm i.d.fused silica capillary.The ratio of the total monomer concentration was adjusted to explore the relation between the ratio and the separation behavior.The results showed that the retention time of the SO42-increased with the larger ratio of the total monomer ,meanwhile the pressure drops increased dramaticly.