Microscopic discharge parameters, such as electron swarm parameters, are important for the in-depth study of gas microdischarge mechanisms. The pulsed Townsend technique has been used to measure the electron swarm parameters, such as the Effective ionization rate coefficient, in SF6–N2 mixture over a wide range of the density-reduced field strength E/N, from 48–660 Td. We discuss the effect of SF6–N2 rationing on electron swarm parameters and density-reduced critical electric field strength (E/N)cr, and evaluate the synergistic effects of the gas mixtures. The SF6 content of the mixture varies between 10%~90%. We observe that the effect of SF6 in the mixture is evident in the effective ionization rate coefficient. When the SF6 concentration in the mixture is high (greater than or equal to 70%), the (E/N)cr is very close to that of pure SF6. The insulation strength of 70% and 90% SF6 in mixture is 0.95 and 0.97 times that of pure SF6, respectively. Our measurements provide fundamental data for modelling the discharge of SF6-N2 mixtures.