Bremsstrahlung emission caused by runaway electrons is widely used in a tokamak as the primary method to determine the time-resolved maximum energy and averaged flux of runaway electrons . This radiation is within the energy range of approximately 0.2 MeV to 20 MeV in the EAST, which produces high-energy hard x-rays. The radiation is dominated by thick-target bremsstrahlung emission when runaway electrons are lost and then hit the limiter or first wall of the EAST.