The utility model discloses a four-line corner support, and solves that a conventional four-line corner support has great limitation in use environment. The four-line corner support comprises a main member and any number of sub-members, wherein the main member comprises an angle iron with a coil holder and a mount which comprises two fixing stripes mutually fixed and integrated. The fixing stripes are provided with fixing holes, and the tail ends of the fixing stripes are provided with positioning grooves. Each sub-member comprises a fixing portion and a prolonged portion, which are mutually fixed and integrated, wherein a positioning block is arranged on the prolonged portion at the end close to the fixing portion, and the other end is provided with a positioning groove. The positioning block cooperates with the positioning groove of the fixing strip or with the positioning groove of the sub-member, and fixing holes are arranged in the fixing portions and the prolonged portions. The mount can be prolonged at will according to needs to adapt to different use environments. The initial length of the mount can be set short to save cost.