A space design for the molecule of hydrocarbon based on the traditional group division method is developed
and a group vector space method (GVSM) for estimating critical property of hydrocarbon is proposed by using the module index of the group vector to characterize the group position in the molecule. Expressions for estimating critical properties Tc
pc and Vc of hydrocarbons are proposed
with the numerical values of relative group parameters presented. The average percentage deviations of Tc