The invention discloses a wall coating roller brush. The wall coating roller brush can supply materials in a directional mode, and brushes a wall uniformly, and coating cannot drip or leak easily. A roller is arranged in the roller brush; a storage cavity is formed in the roller; through discharging holes are densely distributed in a wall of the roller; two ends of the roller are respectively provided with fixing rings and end caps; a shaft hole is formed in the center of each end cap; a center shaft is a hollow shaft, is positioned on the inner sides of the end caps and is provided with a plurality of air outlet holes along the longitudinal direction; step shafts are respectively arranged at opposite positions of inner sides of center holes of the end caps; the excircle of each step shaft is matched with an air flow guiding sleeve of which the cross section is in the shape of a C-shaped opening; guiding plates are respectively arranged at two ends of the C-shaped opening of each air flow guiding sleeve, and are in the shape of a horn mouth; and a counter weight is arranged on the lower portion of each air flow guiding sleeve. When a user brushes the wall by rotating the roller, air flows through the horn mouths and then is blown to the wall, coating is supplied in a directional mode, sagging caused by the reason that the amount of supplied coating is excessive is avoided, the wall is brushed uniformly, and the coating cannot drip or leak easily.