Disclosed is an elastic electroencephalography dry electrode, comprising an electrode base and a plurality of dry electrode units, which are fixedly arranged on the electrode base, wherein each dry electrode unit comprises an elastic supporting element and at least one electrode probe element; one end of the elastic supporting element is fixed to the electrode base, and the other end thereof is connected to the electrode probe element; the electrode probe element is used for being in contact with a scalp to collect an electroencephalography signal; the elastic supporting element is used for transmitting the electroencephalography signal; and the electrode base comprises an electrode substrate element, an electrode unit fixing element and an electrode displacement limiting element. Further disclosed are an electroencephalography device and an application system.