The full-parameter geometry optimization of cationic （ S ） - BINAP - Ru （ Ⅱ ） halide complex was performed by DFT method using B3LYP, PW91 and PBE potentials with several basis sets. PW91 with 3-21G / SDD basis sets is found to be the most suitable method with consideration of both precision and efficiency. The dihedral angles （ θ ） of the binaphthyl or biphenyl with different phosphorus ligand - Ru （ Ⅱ ） halide complexes were found changing from 59.9 to 79.3 degree, while the natural bite angle （ βn ） of those complexes only changes from 87.4 to 90.3 degree. It is different from the common view of asymmetric organic chemists＇ that θ directly influences βn.
