Abstract: Porous carbon was prepared by bituminous coal with different metamorphism degree and used K2CO3 as activators by flash Joule heating under different voltage. The effects of metamorphism degree of the bituminous coal and flash voltage on pore characteristics and crystal structure of porous carbon were investigated and characterized by a series of methods such as field emission scanning electron microscopy (FESEM), low temperature nitrogen adsorption and Raman spectra. Results show that the pressure effect and thermal expansion effect caused by the instantaneous high temperature through the Joule heating in the limited space are the driving forces for the pore formation and expansion. When the alkali-carbon ratio is 3∶1 and the flash voltage is 80 V, the pore structure of the porous carbon prepared from low metamorphic Shuozhou coal is the most developed with the specific surface area is 601.95 m2/g and pore volume is 0.44 cm2/g. The graphitization degree of porous carbon prepared from Changzhi coal with high metamorphic degree is the highest when the alkali-carbon ratio is 3∶1 and the flash voltage is 160 V.