The invention provides a foamed cement heat preserving plate, a coal ash aluminum extracting residue composite for preparing the same, and a manufacture method of the foamed cement heat preserving plate. The coal ash aluminum extracting residue composite comprises the following components in parts by weight: 50 to 70 parts of cement, 25 to 40 parts of coal ash aluminum extracting residue, 2 to 5 parts of exciting agent, 4 to 7 parts of foaming agent, 0.006 to 2 parts of foam stabilizer, and 40 to 60 parts of water. The manufacture method is characterized in that monox and aluminium oxide in the coal ash aluminum extracting residue are subjected to a hydration reaction with calcium hydroxide released by hydrating the cement so as to form a hydraulic material; the exciting agent excites the activity of the coal ash aluminum extracting residue to react. The foamed cement heat preserving plate manufactured by the prepared coal ash aluminum extracting residue composition has the advantages that various performance parameters, such as the density, heat conductivity coefficient and compressive strength meet the requirements on the main performance indicators of the type I foamed cement heat preserving plate as specified by Su JG/T041-2011 Technical Regulations for Application of External Heat Preserving System of Composite Foamed Cement Plate External Wall.