Abstract: Based on the characteristics of molecular topological structure of linear alkane substituted derivatives, linear alkane substituted derivatives were divided into linear chain unit and substituted groups. Then according to the characteristics of the topological structure of each part, the formulae for the calculation of Wiener index have been given. So a new and simple algorithm for calculating Wiener index has been proposed, which simplified the calculation of Wiener index. This new algorithm has the advantages of high efficiency, accurate compared with that of the traditional algorithm for Wiener index, and can be easily used in computer program for Wiener index. Thus the practicability of Wiener index has been improved.

Key words: Substituted derivatives of linear alkanes, Wiener index, Site index, Algorithm