The invention discloses a sealing device of a fluorescent tube, comprising a sealing sleeve, wherein the sealing sleeve is sleeved on the fluorescent tube in interference fit and is internally provided with a main socket body, the main socket body is closely matched with the sealing sleeve and is provided with a conducting connector assembly, and the conducting connector assembly is provided with a through hole used for being inserted by a plug pin arranged on the tube head of the fluorescent tube; the sealing sleeve is also connected with a power wire, the power wire is hermetically matched with the sealing sleeve, and conductor wires inside the power wire are respectively connected with the conducting connector assembly. The sealing device is separated from the fluorescent tube, when in use, the sealing device is sleeved with the fluorescent tube so that the fluorescent tube is suitable for an environment with high humidity or an environment easy to sprinkle by rainwater, thereby achieving the water-proof and damp-proof effect; in addition, when the sealing device is used for drier environments, such as a bedroom, an office, and the like, the sealing device can be used as a common fluorescent tube only by taking the sealing device away, thereby being suitable for the different requirements of customers with one product. Besides, the invention has simple structure and low manufacturing cost.