The invention discloses a length-adjustable rod piece, which comprises a rod body and two end plates respectively arranged at two ends of the rod body; two fixing holes are respectively formed in the middle parts of two ends of the rod body; sliding grooves are respectively formed in two opposite end faces of the fixing holes; the end face of one end, which faces the rod body, of each end plate is provided with a fixing rod which can be embedded into the corresponding fixing hole; the end faces of two ends of each fixing rod are respectively provided with a cylindrical fixing end; the fixing ends can slide along the corresponding sliding groove; a connecting pipe is arranged between the rod body and each end plate; the connecting pipes are in threaded connection onto the rod body. According to the length-adjustable rod piece disclosed by the invention, by adopting a structure of the fixing rods and the fixing holes, the extension of the rod piece is realized; meanwhile, by adopting a sliding groove structure, while extending relative to the rod piece, the end plates cannot rotate relative to the rod piece, therefore the structure is helped to remain stable.