The invention relates to a wall connecting piece of a plug-in type low-carbon heat preservation energy-saving board, which comprises expansion bolts and connecting pieces and is characterized in that the connecting piece comprises a hollow plug-in pipe and a plurality of blocks of right angle type angle steels, the cross section of the plug-in pipe is of a rectangular shape, the inner diameter ofthe hollow part of the plug-in pipe is in plugging fit with each angle steel, the outer surface of the plug-in pipe is provided with a plurality of protruding ridges, and two right angle surfaces of each angle steel are respectively provided with a mounting hole. The invention has the advantages that installation process is simple and fast, special matched adjustable dry hanging connecting piecesare provided, and the hollow plug-in pipe is embedded in a plane material decorative layer in advance, which ensures that the installation process is firm and reliable, saves labor and time, shortensworking period and greatly reduces installation cost. The invention is particularly suitable for old wall reformation, can be directly applied to an old wall face no matter the old wall surface layeris face bricks or coatings, thereby avoiding pollution to the environment due to primary wall face removal, reducing rubbish clearing and delivery, greatly accelerating construction progress and effectively reducing construction cost.