The invention relates to a troffer keel and a mortar smearing processing structure. The troffer keel comprises a suspender, a full-lightweight steel joist structure and a troffer box, and the full-lightweight steel joist structure comprises a main keel, a first-side keel, a second-side keel, a third-side keel, a vertical secondary keel and a horizontal secondary keel; an upper cross plate of the troffer box horizontally extends outwards to form a flat-convex section, the flat-convex section is 10 mm longer than a gypsum trim strip in the horizontal direction, and is covered by an angle shaft strip, and the inner side of the whole troffer and the upper portion of the upper cross plate form a mortar smearing layer through mortar smearing treatment. The full-lightweight steel joist structure is adopted, the structure is stable, and the troffer is not broken after being used for a long term. The flat-convex section of the upper cross plate is covered by the angle shaft strip, burrs of the gypsum trim strip can be shielded, the trim effect is improved, so that the troffer looks fancier, and the lines are smooth. Through the method of forming the mortar smearing layer on the inner side of the whole troffer and the upper portion of the upper cross plate through the mortar smearing treatment, the degree of finish inside the troffer is high, the troffer is clean and attractive, and aftertreatment is facilitated.