The invention belongs to the technical field of building machinery, and particularly relates to a flat jet flow nozzle and a special coating machine which are used for coating various materials on surfaces of the inner wall and the outer wall of a building. The flat jet flow nozzle comprises a shrinkage pipe section, a throat pipe section and a diffuse pipe section from left to right in sequence, the shrinkage pipe section is in a hollow cone shape, the cone angle alpha is in a range being greater than or equal to 30 degrees and less than or equal to 120 degrees, the length of the shrinkage pipe section a is in a range being greater than or equal to 8mm and less than or equal to 30mm, the throat pipe section is in a hollow cylinder shape, the length of the throat pipe section b is in a range being greater than or equal to 1mm and less than or equal to 4mm, an inner cavity of the diffuse pipe section is a flat hole which is formed in a way that the tail of an inner cavity of the throat pipe section gradually transits to the end surface of the tail end of the nozzle, the length of the diffuse pipe section c is in a range being greater than or equal to 3mm and less than or equal to 12mm, the height of the flat hole d is in a range being greater than or equal to 3mm and less than or equal to 12mm, and the width of the flat hole e is in a range being greater than or equal to 1.5mm and less than or equal to 6mm. In the nozzle and the coating machine which are provided by the invention, the coating effect is uniform and smooth, the bonding degree of the materials and a wall body is high, the compactness of the materials is high, the coating efficiency is high, the coating quality is ensured, and further the special coating machine is wide in application range, obvious in economic benefit, and is beneficial to popularization and application.