The utility model provides a water shortage alarm device of a boiler, belonging to the technical field of machinery and solving the technical problems that the existing boiler is inconvenient to supply water, cannot supply water timely and the like. According to the water shortage alarm device of the boiler, the boiler comprises a boiler body, the water shortage alarm device comprises a liquid level controller, a PLC (Programmable Logic Controller) and a sounder, a low level probe and a high level probe of the liquid level controller are both arranged in the boiler body, and the high level probe is positioned above the low level probe; and the liquid level controller and the sounder are both connected with the PLC. The water shortage alarm device of the boiler has the advantages of alarming more timely, supplying water more timely, being better in water supply effect, and the like.