A device for in-situ measuring electrical properties of a carbon nanotube array comprises a chamber, a substrate, a first electrode, a connecting wire, a second electrode, a support structure, and a measuring meter. The substrate, the first electrode, the connecting wire, the second electrode, and the support structure are located inside of the chamber. The measuring meter is located outside of the chamber, and the measuring meter is electrically connected to the first electrode and the second electrode. The first electrode defines a cavity, and the substrate is suspended in the cavity by interaction of the support structure, the second electrode, and the connecting wire.