Abstract: In order to prepare some quality tantalum film for the study of high temperature and high pressure equation of state (EOS), the electropolishing of tantalum was carried out in sulfuric acid-methanol electrolyte. The test results of root mean square roughness and surface topography confirm that tantalum can be polished in this electrolyte. The effects of electrolyte composition, cell voltage, temperature and stirring rate on the surface roughness of electropolished tantalum were discussed. The results show that the optimal conditions are as follows: Sulfuric acid and methanol in volume ratio is 1∶7, cell voltage is 15-20 V, temperature is -100 ℃ and stirring rate is more than 8 m/s.