An electrostatic discharge (ESD) and testing composite component, an array substrate and a display device are provided. The composite component includes a first signal line, a first thin-film transistor (TFT) and a second TFT which are electrically connected with the first signal line, a second signal line electrically connected with the first TFT, and a third signal line and a fourth signal line which are electrically connected with the second TFT; and the composite component is configured to provide a testing signal for the first signal line at a first stage and configured to provide ESD for the first signal line at a second stage, and the first stage is a testing stage and the second stage is an ESD stage. The composite component occupies small area and acquire a narrow-bezel and/or high-resolution display panel.