Sagdeev’s Quasipotential approach is extremely suitable for studying large amplitude solitary waves in plasma. One can derive all the one soliton results of perturbation methods and can compare it with the exact results obtained by the Quasipotential (also called the pseudopotential) method. However comparatively fewer works in relativistic plasma and plasma with trapped electrons have used this method. In this paper the pseudopotential is derived for a relativistic plasma with non-isothermal electrons and finite temperature ions. Expanding the quasipotential different types of solitons are obtained which agree with the perturbation results. Also the relativistic effect and finite ion temperature appear to restrict the region of existence of solitary waves.