Relativistic electrons are produced, with energies up to 10 MeV, by the interaction of high-intensity laser pulse with an underdense plasma. With the progress of short-pulse multi-terawatt laser, it has become possible to produce MeV electrons in a plasma. These electrons can be used to apply to medicine and technology. Three-dimensional (3D) particle-in-cell (PIC) simulations were performed to produce supra-thermal electrons.