The invention provides a method and a device for determining parameters of a high-speed earthing switch along a half-wavelength transmission line. The method comprises steps of firstly determining a high-speed earthing switch required for action along a half-wavelength transmission line, and then operating the high-speed earthing switch required for action, and finally obtaining parameters of thehigh-speed earthing switch. The invention provides the action control process of the high-speed earthing switch arranged along the line when a single-phase earth fault occurs at different positions along the half-wavelength transmission line, so that the high-speed earthing switch can be reliably operated, the phenomenon that the secondary arc cannot be reliably extinguished caused by the malfunction of the high-speed earthing switch is avoided, the secondary arc current and the recovery voltage in the half-wavelength transmission line single-phase reclosing process can be effectively reducedto ensure the success rate of reclosing. The invention obtains different switching on and off conditions of the high-speed earthing switch and rated induction voltage and rated induction current of the high-speed earthing switch in the switching on and off process, and provides a technical basis for the selection of the high-speed earthing switch.