In this paper,the structure and dissociation energy of the ground state of BiH （D,T） are investigated by quantum mechanical ab initio method in the level QCISD/ LanL2DZ methods. Based on the theory of atomic and molecular statics, the reasonable dissociation limit for the ground state （X3Σ-）　of BiH　（D,T） is derived. The potential energy curve and relevant optical constants of this state are obtained by least square fitting to the Murrell-Sorbie function. All calculation results are in good agreement with the experimental data.