A hollow slab of cast-in-place reinforced concrete consists of reinforced concrete (RC) and cavity die-shell wrapped in RC and arranged alternatively. It is featured as setting cast-in-place RC rib between cavity die-shells, using top plate and peripheral side wall as well as bottom of cavity die-shell to form polyhedral closed cavity with horizontal groove on peripheral side wall, setting horizontal reinforced wire in said groove, forming female angle at one of horizontal corners on bottom portion between said wall and said bottom, forming flange on female angle by cast-in-place concrete so as to form rib in inverted T form on relevant said rib. |