Abstract: The equilibrium structure of the ground state X1Σ+ of AsP have been calculated using many methods and basis sets. The conclusion is gained that the method B3LYP/6-311++G(3df,3pd) is the most suitable for the energy calculation of AsP by comparing the experimental data. The harmonic frequency and whole potential curve for the ground state of AsP is further scanned using this method, then have a least square fitted to Murrell-Sorbie function, and last the spectroscopy constants are calculated, which are in better agreement with the experimental data. It is believed that MurrellSorbie function form and B3LYP/6-311++G(3df,3pd) method are suitable for the ground state of AsP.