Abstract: The numerical research about the orbital evolution of NEAs has been made by adopting the improved explicit Symplectic Algorithm. For the mechanic model, Post-Newtonian effect has also been taken into account, apart from considering the gravitational perturbations of major Planets, while for the algorithms the investigation focuses on the applicable prospect that the Symplectic Algorithm would be suitable for the study of the orbital evolution of the NEAs, especially for the effectiveness of the Symplectic Algorithm in the case that the NEAs close approach a major planet.