The experiments of high pressure torsion(HPT) subjected to tungsten were conducted under 1 turn, 2 turns, 5 turns and 10 turns at 550 ℃. The microstructures of sintered and HPT-processed tungsten were characterized by electron backscatter diffusion(EBSD) and transmission electronic microscopy(TEM). Results show that the grains of sintered tungsten were refined and the propotion of high angle grain boundary increased. Meanwhile, the dislocations were moving towards the grainboundary and rearranged orderly during HPT process. The grain boundary energy of sintered and HPT-processed tungsten were calculated by modified dislocation model. It was found that the grain boundary energy kept increasing and it was main from the excess dislocation energy. Also, the non-equilibrium grain boundary was observed. It is only formed in nano-materials that is prepared by severe plastic deformation. In high resolution TEM,it shows the features of thick grain boundary thickness and moire fringes caused by crystal plane interference.