CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly altatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I tary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis,compared with SF6 gas mixtures.The results confirm that the critical electric field strength of CF3I/c-C4Fs/70 ％ CO2 is greater than that of 30％ SF6/70％ CO2 when the CF3I content is greater than 17％.Moreover,a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field,and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures.The synergistic effects for CF3I/c-C4Fs/70 ％ N2 were most obvious when the c-C4F8 content was approximately 20％,and for CF3I/c-C4Fs/70 ％ CO2when the c-C4F8 content was approximately 10％.On the basis of this research,CF3I/c-C4F8/70 ％ N2 shows better insulation performance when the c-C4F8 content is in the 15％-20％ range.For CF3I/c-C4F8/70 ％ CO2,when the c-C4F8 content is in the 10％-15％range,the gas mixtures have excellent performance.Hence,these gas systems might be used as altative gas mixtures to SF6 in high-voltage equipment.