In this work, a low-cost and high resolution X-ray micromask is developed by sputtered lead film on Mylar sheet substrate with lift-off process and the X-ray mask is experimented for patterning SU-8 negative photoresist on glass substrate. Sputtering is selected for Pb thick film deposition due to its high sputtering yield. The Pb mask is used for X-ray lithography of SU-8 photoresist with 5 m closely spaced square array patterns, designing for electrowetting electrodes on microfluidic chip. For 140 m-thick SU-8 photoresist, Pb film thickness of around 10 m was used to block X-ray with 95% X-ray image contrast at a critical dose of 4,200mJ/cm3. A high aspect ratio of 26.5 of SU8 microstructure with 5 µm lateral resolution has been demonstrated by the developed low cost Pb based X-ray mask. In addition, a steep sidewall angle of nearly 90o for SU-8 structure is confirmed. The results demonstrate that the Pb based X-ray mask offers high resolution X-ray lithography at a very low cost. Therefore, it is highly promising for commercial applications.