Abstract: PDMS is the main material for manufacturing microfluidic chips,and the most used method for PDMS fabrication is plastic molding,which requires good plastic mold.SU-8 has been widely applied for MEMS fabrication and plastic mold for PDMS because of its micro-machining characteristics.According to the requirements of mold such as flat,crack-free,and reusable,this paper study factors influencing the cohesion between SU-8 mold structure and silicon substrate and cracks,optimizing the fabrication process of SU-8,in the condition of heat treatment at the rate of 0.5℃/min,dosage at 210 mJ/cm²,and hardbake at 200℃ for 30min,providing a fast,reusable,low cost SU-8 mold manufacturing method for PDMS microchip plastic molding.