Provided are a method and device for controlling electrode plates (21, 22, 23, 24), used for controlling the properties of each electrode plate (21, 22, 23, 24) in a set of electrode plates. The control method comprises the following steps: first, a control-signal receiving terminal (3) receiving a target-property control signal (S101); then, a property information obtaining circuit (4) obtaining target property information of each of the electrode plates (21, 22, 23, 24) according to the target-property control signal (S102); lastly, according to the target property information of each of the electrode plates (21, 22, 23, 24), a control circuit (5) controlling each of the electrode plates (21, 22, 23, 24) to connect to a corresponding target property terminal (S103). When the method and device are used to detect impurities in a substance, it is possible, without adjusting the position of contact between the electrode plates (21, 22, 23, 24) and the test substance, to change, by means of changing the property
