Abstract: A light steel keel connecting structure, comprising at least two light steel keels, each of which has a connecting surface connecting with the other light steel keel, and connecting pieces for connecting the light steel keels, characterized in that concaves are provided on each of the connecting surfaces respectively which are depressed toward inside of the light steel keels, and the concaves of two connecting surfaces which are connected vertically are disposed by way of embedding, and at least two connecting holes are provided at corresponding positions of two concaves that are embedded, respectively, and the connecting pieces are provided within the connecting holes in a state of connection. The terminals of the connecting pieces at one end where depression sides of the concaves are located do not go beyond outer edges of the openings of the concaves on the same side as the terminals of the connecting pieces.