The invention discloses an insulator surface RTV spraying thickness measuring device. The device includes a first lever arm and a second lever arm which are hinged together, a first pressure head and a sensor are arranged on the first lever arm, a second pressure head arranged opposite to the first pressure head and a measuring head arranged opposite to the sensor are arranged on the second lever arm, the device also includes an elastic clamping device used for realizing compaction and contact of the first pressure head and the second pressure head, and the sensor is connected with a signal processing module. In measurement, the two pressure heads are separated and an insulator piece is put between the two pressure heads, a change of distance between the pressure heads is converted to a change of distance between the sensor and the measuring head and a change of a sensing signal through the two lever arms, and the signal processing module can obtain the thickness of the insulator piece through calculation according to the change of the sensing signal. A thickness difference of the insulator piece that is measured before and after spraying RTV is the thickness of an RTV coating. The insulator surface RTV spraying thickness measuring device provided by the invention can accurately and rapidly measure the thickness of the RTV coating without damaging the RTV coating.