The model of the petroleum hydrocarbon pyrolysis process based on free radical mechanism requires analyzing the detailed components of petroleum hydrocarbon.This paper integrated the molecular attributes in the petroleum hydrocarbon and the industrial indices of the petroleum hydrocarbon such as average molecular weight
H/C-ratio
the paraffin
isoparaffin
olefins
naphthenes
aromatics (PIONA)mass fractions and a set of ASTM boiling points and the information entropy theory to predict the equimolecular mixture of the petroleum hydrocarbon.The method was applied in predicting the equimolecular mixture of naphtha and heavy vacuum gas oil.The calculated values of equimolecular mixture were in good agreement with the experiment data and the result proved that this method is effective.