Abstract: The gases commonly used in electrical engineering applications such as SF₆ and air et al are electronegative, so attachment is a key collision process in their streamer discharges. In order to investigate the effects of attachment on electron transport characteristics, electron transport coefficients of model and real electronegative gases were calculated based on multi-term solution of Boltzmann equation. Firstly the effects of the free parameters such as vmax, lmax and Tb on the convergence of the transport coefficients were analyzed. It can be seen that the order vmax of the Laguerre polynomials which is needed to expand the electron velocity distribution function is smallest when T_b is equal to T_b（opt）, and in general all transport coefficients can achieve four-digit accuracy when lmax is increased to 3. Then the modified attachment model of Dujko was considered to investigate the effects of different attachment frequency on the electron transport characteristics. It is shown that the attachment coefficient tends to increase as attachment cross section increases, however the bulk drift velocity, bulk diffusion coefficient and mean electron energy tend to decrease as attachment cross section increases. If the attachment frequency in low-energy region is higher, the bulk drift velocity and mean electron energy are smaller. In the end the transport coefficients of the real gas SF₆ were considered. The flux and bulk drift velocities, mean electron energy, reaction coefficient, flux and bulk diffusion coefficients were obtained. The validity of multi-term solution of Boltzmann equation to obtain the transport coefficients of electronegative gases was demonstrated and the deficiency of experimental method was pointed out when the reduced electric field is small.