The utility model relates to a horizontal mixer with a material level adjusting function. The horizontal mixer comprises a motor, a speed reducer, a rotor shaft, a barrel, a feeding hole and a support, wherein the motor is connected with and drives a rotor in the barrel through the speed reducer; a square material level control box communicated with the barrel is arranged at the right end of the barrel; a material level flashboard capable of moving upwards and downwards is arranged in the material level control box; an electric executor is arranged on the top of the material level control box, and is connected with the material level flashboard through a pin shaft; a discharging hole is formed in the bottom of the material level control box; a group of knife-shaped blades is arranged on the rotor; certain angles are formed between the knife-shaped blades and the axis direction and the horizontal direction of the rotor. As the horizontal mixer adopts a unique rotor blade design, materials are mixed fully, and high mixing efficiency is achieved. Materials are fully mixed after the material mixing level and material mixing time are adjusted dynamically through a material level control valve, so that the material mixing uniformity is enhanced greatly. Moreover, the output per machine hour can be adjusted conveniently according to processes requirement.