Abstract: Based on the introduction of bonding parameters and quantum numbers, an approved atomic valence named δiY was suggested, and a novel molecular topological index mXY was put forward. The approved atomic valence δiY was recommended relating to such atomic properties as Yang’s electronegative force gauge Yi, electron number of valence shell Zi, number of bonding electrons bi and the main quantum number of valence shell ni. The first order index 1XY was utilized to study quantitatively the structure-property or structure-activity relationship of organic and inorganic compounds. The index was correlated with the selected properties or activities of physicochemical properties, as boil point, heat capacity of liquids, heat capacity of vapors, heats of vaporization, critical temperature and critical pressure, of alkanes, the hydrophobicity parameter of phenyl halides, retention index of gas chromatograph of alkoxyl silicon chlorides, the toxicity of heterocyclic nitrogen-containing compounds, the lattice enthalpy of alkaline halides F bands energy of alkaline halides, and 119Sn Mossbauer shift of tin halides. The results suggested that the proposed index with fairly high and extensive correlation ability could be a useful parameter in QSPR and QSAR research.