The molecular structure of alkanes is described by a novel coding method, recently developed in this laboratory, on the basis of molecular subgraph. It has been shown that there exists very good correlation between the coding and thermodynamical functions of alkanes. The correlation coefficients (R) of MLR equation for quantitative structure property relation (QSPR) on Gibbs energy(△Gf), atomization heat (△H_atm), heat capacity(C_p), evaporating enthalpy (△H_V), enthalpy (△H_f(l)) and entropy (S) are respectively 0.9559, 1.0000, 0.9905, 0.9969,0.9973 and 0.9922. The responding derivation (S) are 4.710, 4.307, 3.793, 0.484, 0.931, 0.585.