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As an epoxy-based negative photoresist, SU-8 is being widely used for various permanent use MEMS devices due to its excellent thermal and chemical stability. Due to its UV curability, classical structuring methods of SU-8 are based on UV photolithography and UV imprint processes. This study describes a process to form a micro pattern in SU-8 film that is based on thermal imprinting. One of major obstacles in the process is that SU-8 is easy to deform during and after releasing a mold because the mold is separated from the SU-8 in the un-cured state. In this study, series of imprint tests using a Ni mold were performed with the un-cured SU-8 samples pre-treated with UV light for different exposure time, and their results were compared each other in terms of the replication quality. As a result, a SU-8 sample pre-treated with UV light for 8 s resulted in the best replication quality for given imprint conditions, and we could successfully replicate micro patterns with the aspect ratio of 2.5 (25 mum depth and 10 mum line-and-spacing) in SU-8 resist.