The invention discloses a construction work rack below a roof on the outer side of a prefabricated boundary beam. The construction work rack comprises a hanging basket type work platform and an overturning main frame which is integrally in an L shape. The horizontal section of the overturning main frame is arranged on the top face of the T-shaped prefabricated boundary beam, and the length direction of the horizontal section is parallel to the width direction of the T-shaped prefabricated boundary beam. The bottom of the vertical section of the overturning main frame is fixedly connected with the work platform, an upwards-tilting corner frame is fixedly arranged on the bending part of the L-shaped overturning main frame, and a fixed pulley is arranged at the front end of the corner frame. The bottom of a ladder stand is fixedly connected to the work platform, and the top of the ladder stand is fixedly connected to the bending part of the L-shaped overturning main frame. One end of a locking frame is fixed to the inner side edge of the roof of the T-shaped prefabricated boundary beam, and the other end of the locking frame is hinged to the horizontal section of the overturning main frame. A machine frame is arranged on the locking frame, and a winch device is fixed to the machine frame. According to the construction work rack, construction of the outer side of the boundary beam is safe and reliable, the construction work rack can be in position easily, and operability is high.