The invention discloses a horizontal coating mixing device. The device comprises a cylindrical shell and a variable frequency motor; a rotating shaft is arranged in the cylindrical shell; the rotation shaft is provided with a left spiral blade group and a right spiral blade group; a dosing tube is arranged in the rotating tube;, and the dosing tube communicates with ingredient spray tubes; and a feeding tube is arranged at the right side of the cylindrical shell, the bottom of the cylindrical shell is provided with a discharging tube, and the discharging tube is provided with a solenoid valve. A horizontal stirring cylinder, the opposite spiral blade groups and the ingredient spray tubes positioned between spiral blades are arranged to realize full contact and mixing of ingredients and a semi-finished coating, so the mixing efficiency and the mixing effect are improved, and the quality of a coating is improved; and a foaming agent dispersing tube is arranged to make foams generated in production rapidly eliminated, so the quality and the production efficiency of the coating are improved.