The most important way for understanding the physics of particle is to calculate the scattering amplitude of particles. We can use results of the scattering amplitude to calculate the scattering cross section, that is a desired parameter in experimental particle physics. In this thesis we have calculated the scattering amplitude of some important interaction in QED and QCD using spinor helicity formalism, MHV and little group methods. Starting with the Feynman rules and converting them to the spinor helicity formalism, we calculated the scattering amplitudes. Using these methods makes the computation much simpler.
