The present work devotes to the energy levels of positron under molecules XH(X=O, S, Se and Te)and the relations with nuclear field using Dirac equation based on the full symmetry group. Under these nuclear fields, the energy of positron is about e+=-1.022 MeV. For the lower energy level, the energy of positron is increased with nuclear field; for the higher energy level, the energy of positron is nearly invariant with nuclear field. In this case, it is the three-photon annihilation. The formation of the positronium is in orthopositronium 3S, excited state, followed the conservation of charge parity.