The elastic collision cross-section is a key parameter in the study of inter-particle interactions, which helps to reveal the microscopic mechanism of gas insulation. For this reason, the elastic collision cross-sections of 24 gas molecules at 0-15 eV are calculated based on the R-matrix theory, and cross-section characteristic parameters of the lowest resonance state energy and its peak are extracted. Then the calculated and experimental values of SF ₆, CF ₂Cl ₂, and i-C ₃F ₇CN cross-sections are compared, and the low-energy cross-section data of i-C ₃F ₇CN at 0~1 eV are given for the first time. Furthermore the effects of Cl-substitution and carbon chain length on the cross-section parameters were analysed. Finally the correlation between cross-section characteristic parameters and insulation strength was investigated. The results show that the lowest shape resonance state energy for each molecule is in better agreement with the data from existing studies, with a mean square error of 0.181. F-substitution, the resonance energy gradually increases and the peak value gradually decreases; carbon chain extension is the opposite, the resonance state energy gradually decreases and the peak value gradually increases; The lowest resonance energy and peak value are strongly correlated with the insulation strength. The lower its lowest resonance energy and the larger the corresponding peak value, the higher the molecular insulation strength. Relevant data can theoretically complement existing experimental data. This study provides low energy cross-section properties of a wide range of insulating gas molecules, which can be useful for qualitatively evaluating the insulating properties of gas molecules, and thus for rapid screening of SF ₆replacement gases.