The utility model discloses a mixing device in an automatic feed brick pressing system. The device comprises a horizontal mixing tank and a helical ribbon stirrer rotationally limited in the middle ofthe mixing tank, the key point is that the cross section of the mixing tank is U-shaped, the top of the mixing tank is hinged with a full-open top cover, the bottom of the mixing tank is provided with an automatic flap door driven by a cylinder, a discharge port covered by the automatic flap door is communicated with a feed port of an automatic feeding machine by virtue of a guide chute, and a discharge port of the automatic feeding machine is communicated with a filling hopper of a press machine. According to the mixing device, the feeding mode and the discharging mode are adjusted so that the automatic feeding machine can be in butt joint with the press machine, the mixing procedure and the pressing procedure of feed can be connected, materials with the good mixing effect can be stablyand efficiently provided for the pressing procedure, and therefore the automation degree and efficiency of feed brick pressing are improved. Under the condition that a mixture is not damaged, composite motion such as cross convection, mixing and diffusion is generated in the mixing tank, materials can be turned over to the maximum extent, and the mixing effect is good.