The utility model provides a light steel centre keel and subassembly thereof, the cross section of light steel centre keel is the U style of calligraphy, the first side of U style of calligraphy is provided with inward first hem, be provided with U type recess on the first hem, be provided with inward second hem on the second side of U style of calligraphy, the base interval of U style of calligraphy is provided with at least two U types arch, wherein, with the U type that the second side the is adjacent arch of U style of calligraphy is first arch. The utility model provides a light steel centre keel and subassembly thereof, its simple structure, easily processing, the equipment is simple, through setting up recess and arch, can effectively increase the support intensity of light steel centre keel self, and per two its recesses of the equal accessible of light steel centre keel establish with the protruding card that corresponds, and the combination forms supports the stronger light steel centre keel subassembly of intensity, can satisfy the support intensity demand of the structure of having relatively high expectations in partition wall edge, door and window edge etc..