A novel method based on disposable agar hydrogel temples have been developed for the fabrication of PMMA microfluidic chips. Molten agar hydrogel was sandwiched between a glass plate and a PMMA template bearing negative relief of microstructure. After cooling, the negative PMMA template could be easily separated from the solidified agar hydrogel and a layer of agar hydrogel temple bearing high-fidelity positive relief of the microstructure was left on the glass plate. Prepolymerized methyl methacrylate molding solution containing ultraviolet-initiator was subsequently sandwiched between the agar hydrogel template and a PMMA plate and was allowed to polymerize under ultraviolet light to fabricate the PMMA channel plate at room temperature. Complete microchips could be obtained by bonding the channel plates with covers. The prepared microfluidic microchips have been successfully employed in the electrophoresis separation and detection of several ions in connection with contactless conductivity detection.