A formulated as Δ fH ○[KG-1][KG-2] —? (PDDs,g)= a + b iP i + c if i is put forward for estimating standard formation enthalpies of pyridine derivatives (PDDs),in which, P i is path index and c if i is an amended term of interaction between substituent and N atom on pyridine ring. The Calculations based on the model were carried out for some pyridine derivatives.The values of standard formation enthalpy calculated are consistent with those in literature A formulated as Δ fH ○ [KG-1] [KG-2] - · (PDDs, g) = a +  b iP i + The Calculations based on the model were carried out for some pyridine derivatives. The values ​​of standard formation enthalpy calculated are consistent with those in literature