The utility model discloses a lime dissolving device, comprising a lime dissolving tank, a slaker, a conveying machine, a charging hopper and a blower fan. A paddle valve is provided beneath the charging hopper, and is communicated with the conveying machine which is connected with one end of the slaker via a feeding pipe; the other end of the slaker extends into the lime dissolving tank; the lime dissolving device is also provided with an air inlet device for the air, comprising a main body, an upper pipe, a lower pipe, an upper guide plate and a lower guide plate; the main body is a cavity structure, and is provided with an air inlet; the upper pipe and the lower pipe are arranged in the cavity of the main body, and are respectively communicated with the feeding pipe, the feed pipe of the slaker; a gap is provided between the upper pipe and the lower pipe; the upper guide plate and the lower guide plate are respectively slantingly arranged on the ports of the upper pipe and the lower pipe; a quantitative blanking pore plate is provided above the paddle valve of the charging hopper. Due to the fact that one air inlet device for the air is added on the inlet pipe of the slaker by the lime dissolving device, the air is made enter into the feed pipe of the slaker, and the moist air generated in the slaker is extruded from the feed pipe of the slaker, and is completely discharged by an exhaust air fan, which avoids the lime being wetted, and the problem that the position of the feed pipe of the slaker is easy to be blocked is solved.