Abstract: A new method for rapidly and accurately measuring the electron-drift velocity was described in detail. This method is based on analyzing the induced signals of double grid of an ionization chamber to determine the electron-drift time between the two grids. The waveform digitizer was employed to record pulses from the two grids of the ionization chamber. The electron -drift velocity was measured as the function of the reduced electric field for 8 different ratios of argonmethane mixtures. A formula for calculating electron-drift velocity in any ratio of argonmethane mixtures was presented.