In this paper, the value of delta in molecular connectivity method was weighted by Mulliken bond order, it connected the molecular orbital theory with the topological theory effectively and converted the molecular connectivity method to a novel quantum-topology method. Comparing the value of delta of molecular connectivity with the Mulliken bond order could find that they have similar physical meanings, but the Mulliken bond order had its own advantage. Some typical hydrocarbons were calculated by the novel molecular connectivity index, the result showed that they have good correlationship with their volume, hydrophobic parameter and thermodynamic properties.

Key words: TOPOLOGY, MOLECULAR ORBITAL THEORY