This thesis studies the quantum transport mechanism by developing a quantum transport program using NEGF method. In recent years, transistors have been scaling down below 20 nm. The traditional carrier transport program which using drift-diffusion model can no longer accurately describe the transport phenomenon because it ignores the quantum wave pictures. As a result, a program studying carrier transport based on the quantum field theory is required. In our program, we specify the nanowire structure which is a promising solution to suppress short channel effects in small scale device. The key feature is that we successfully include optical phonon, acoustic phonon, surface roughness scattering in the NEGF solver which can simulate the energy relaxation in different energies and the transition rate to the different states in the nanowire.