We measured the electron drift velocity, W, in 0.5% $SF_6-Ar$ mixture over the E/N range from 30 Td to 300 Td and gas pressure range from 0.1 to 0.5 Torr by the double shutter drift tube with a variable drift distance, and calculated over the same E/N and gas pressure range by using the two-term approximation of the Boltzmann equation. The measured and calculated values at different gas pressure at each E/N was appreciable dependence in the results on the gas pressure.