Abstract: In this paper, according to the peak numbers of the nuclear magnetic resonance and the Randic embranchment degree (δ_i) of carbon atom i, the carbon atom’s environment valence gi is defined as: g_i=(t_i+δ_i)/2.The g_i reflect the characteristic of each carbon atom, and as well as the conjunction detail of the carbon atom with other carbon atoms.So, the gi could distinguish better the chemical environment of each carbon atom in the molecule than δ_i.A connectivity index of environment valence (^mS) and its athwart index (^mS′) are proposed based on the adjacency matrix and the carbon atom’s environment valence gi.Among them, the ⁰S and ⁰S′ include the characteristic and the connectivity of each carbon atom, the ¹S and ¹S′ reflect the second conjunction between carbon atoms.Based on ⁰S′ and N(the number of carbon atom), a new structural parameter——symmetry degree (N_ec), is defined as: N_ec=［(⁰S′_S/⁰S′_C)N］^2/3,and the N_ec reflect the size of the molecule as well as the symmetry of the molecule.The N_ec, ⁰S and R_n(the biggest ring’s edge numbers of cycloalkanes) of 474 saturated hydrocarbons (216 paraffins and 258 cycloalkanes) were calculated and correlated with their boiling points.The best regression equation was obtained as follow: ln(1056-T_b)=6.9480-0.1040N_ec -0.008689⁰S-0.009614R_n+0.01998R^0.5_n,n=474,R=0.9989,F=52627,S=5.63K.The model was checked up by the Jackknife’s method.It should have overall steadiness and could be used for predicting the boiling point of saturated hydrocarbons.