Disclosed is an electro-static discharge (ESD) protection unit, an array substrate, a display panel and a display device. The electro-static discharge protection unit comprises n stages of thin film transistors connected in series, wherein n≧2, a control electrode of each stage of thin film transistor is floating, a source electrode of a first stage of thin film transistor is connected with an electro-static generation terminal, a drain electrode of each of the first to n−1th stages of thin film transistors is connected with a source electrode of a next stage of thin film transistor, respectively, and a drain electrode of a nth stage of thin film transistor is connected with an electro-static discharge terminal; or wherein n≧3, a control electrode of each stage of thin film transistor is floating, a source electrode of a first stage of thin film transistor is connected with a first electro-static generation terminal, a drain electrode of each of the first to n−1th stages of thin film transistors is connected with a source electrode of a next stage of thin film transistor, respectively, and a drain electrode of a nth stage of thin film transistor is connected with a second electro-static generation terminal. The ESD protection unit can still protect signals in an electro-static generation terminal from being interfered when the thin film transistor adjacent to the electro-static generation terminal is broken down due to ESD, thereby avoiding failure due to ESD.