Catalysts based on the Earth abundant transition metals are commonly seen in the chemical and biologic reactions. The reactivity of the catalyst is determined by the orbital interaction between the transition metal and ligand groups. In order to understand the role of transition metal in the catalysis, the core level spectroscopy can be used to target the valence orbitals by exciting electron from the core orbitals to the valence shell. For investigating the electronic structures of the target molecules, the high level theoretical method is required, the restrict active space (RAS) method can handle all important spectral effects very nicely, such as multiplet structures, spin-orbit coupling, charge-transfer excitations, and ligand field splitting. To model different types of core level spectroscopy, the orbitals of interest can be included in the different subspace, the electron excitation can be restricted by specifying the minimum number of hole in RAS 1 or the maximum number of electrons in RAS3. We believe that the simulation and interpretation of the measured different types of X-ray spectroscopy can provide useful guides to the catalyst design.