A novel technique to bond polymer substrates using PDMS-interface bonding is presented in this paper. This novel bonding technique is promising to achieve precise, well-controlled, low temperature bonding of micro fluidic channels. A thin (10-25μm) Poly(dimethylsiloxane) (PDMS) intermediate layer was used to bond two polymer (PMMA) substrates without distorting them. Micro channel patterns were compressed on a PMMA substrate by hot embossing technique first. Then, PDMS was spin-coated on another PMMA bare substrate and cured in two stages. In the first stage, it was pre-cured at room temperature for 20 hours to evaporate the solvents. Subsequently, it was bonded to the hot embossed PMMA substrate. In the second stage, PDMS was completely cured at 90°C for 3 hours and the bonding was successfully achieved at this relatively low temperature. Tensile bonding tests showed that the bonding strength was about 0.015MPa. Micro fluidic channels with dimensions of 1mm×2cm×1mm were successfully fabricated using this novel bonding method.