Abstract: An atomic colouring number (f_i) defined on the basis of the syst ematic n omenclature principle of organic compounds and the structure characteristics of bonding atoms has excellent selectivity for non-hydrogen atoms in alkanes and alkyl derivative molecules. On the basis of adjacency matrix, two novel connec tivity indexes (^mQ and its converse index ^mQ^ ) are constructed from f_i. The boiling points (Ｔ_b, K) of 85 alkanes can be expressed by means of ^０Q1Qand δ_max (the largest point valence of carbon atom): ln(714-Ｔ_b)=－0.1472 ^０Q－0.0041¹Q+0.0089δ_max+6.5164， R=0.998　9； A satisfactory function for 72 aliphatic aldehydes and alkanones is established, i.e.： ln(693-Ｔ_b)=－0.2267^{1< /sup> Q－0.00671Q+0.0301δ_max+6.1425， R=0.999　0. The boiling points for above mentioned 157 organic compounds are expressed as： ln(690-Ｔ_b)=－0.0320０Q+ 0.0005 1Q+0.0195δ_max+6.1590， R=0.99 7　6. Their correlativities are more ideal than those by the literature method s. It is concluded that the indices bear good structure selectivity and property rel ativity. For this new method the calculation is convenient and the result is accurate.}

Key words: atomic colouring number, connectivity index, converse index, alkane, a liphatic aldehydes and alkanones, boiling point, QSPR model