The invention provides an arrester overvoltage protection device with a variable voltage ratio and an implementation method, belonging to the technical field of power electronics. The device comprises an arrester serial connection group, a thyristor system and a fault detection system; the thyristor system is connected in parallel with an arrester in the arrester serial connection group; and the fault detection system is connected in parallel with the arrester serial connection group. The arrester overvoltage protection device with the variable voltage ratio has a relatively small number of used parts, a simple structure and a small floor area. In addition, as the power electronic devices used by the device are low in cost, the arrester overvoltage protection device with the variable voltage ratio lowers comprehensive manufacturing cost of a whole set of device, gives a consideration to economical efficiency and practical applicability, and has relatively good application foreground.