The utility model belongs to the technical field of the transformer, concretely relates to oil level gauge, including the oil level gauge casing, the oil level gauge casing in be provided with the oil level scale, the oil level gauge casing is provided with the oil of connecting on the oil level scale through the connecting rod outward and floats, the oil level gauge casing passes through threaded connection and links to each other with transformer tank, the oil level gauge casing is equipped with the cylinder installation screens that is used for installing the oil level gauge casing being close to oil level gauge shell external thread department, is equipped with prism installation screens in the cylinder installation screens one side of keeping away from oil level gauge shell external thread. The utility model discloses prism installation screens of design on oil level gauge, dismantlement, installation that the use breakout tongs just can be convenient, the breakout tongs is the instrument that the popularity is very high, the convenience is look for and is purchase. In the maintenance in later stage is maintained, do not need special instrument, user oneself just can install, dismantle oil level gauge, the ease for operation and the security of the maintenance that improves greatly.