Dimethylphenylsilanol is easily refined into high pure silicon, but there is a lack of experimental data of its chemical bonding properties. The optimized molecular structure parameters of dimethylphenylsilanol are calculated through density functional theory (DFT) method with B3LYP/6 311++G** basis sets. Then, the molecular chemical bonding properties are investigated with the natural atomic obtain analysis, the frontier orbital analysis and the overlap population analysis under the natural bond orbital (NBO) theory. It is showed that the O-H bond isn’t affected when the phenyl and the methyl are joined into molecule, but the molecular energy and dipole moment are reduced, so as to make molecule more stable. The Si-C bond between silicon atom and the phenyl is weak. But the bond strength of Si-O is strengthened a little. The O-H bond is the weakest one in the molecular chemical bond. In addition, the electron on the carbon atom in the phenyl is prone to nonlocalizing primarily. The lone pair electron of oxygen atom transferring to the anti bonding orbital between silicon and carbon atoms weakens Si-C bond to some sort. So the gap of the theoretical principle of chemical bonding properties of C6H5(CH3)2SiOH can be filled and the basic theory of chemical reaction of C6H5(CH3)2SiOH is obtained.