A slurry mixing device includes an installation frame, a slurry mixing tank, a slurry feeding tank, a cooling mechanism and a slurry discharging mechanism. The slurry feeding tank is movably arranged under the slurry mixing tank, the cooling mechanism and the slurry discharging mechanism. A mass scale is arranged under the slurry feeding tank. A stirring cavity is formed in the slurry mixing tank, and a stirring paddle is arranged in the stirring cavity. A stirring motor is arranged on the slurry mixing tank. An outlet is arranged on the bottom of the stirring cavity. An oil bath cavity is formed between the slurry mixing tank and the stirring cavity. The cooling mechanism includes a lifting cylinder and a lifting base. The lifting base is provided with a rotating paddle and a rotating motor. The lifting cylinder is arranged on the installation frame.