Buildings energy conservation is an important issue in the current world. The inorganic foam material has become one of main developing directions in the field of energy engineering due to its multifunctions such as thermal insulation, sound insulation and fire prevention. The preparation technology of geopolymer foamed composite was studied by introducing industrial waste residue fly ash into Portland cement. The influences of water cement ratio, foaming agent, polycarboxylate superplasticizer and alkali compound excitation agent on the forming, density and strength of cement foam were explored. The geopolymer foamed composite with density of about 0.8 g/cm3 and compressive strength of 2 MPa has been prepared successfully by using fly ash and cement as main raw materials, H2O2 as foaming agent, polycarboxylate as superplasticizer, sodium dodecyl sulfate (SDS) and hydroxyethyl cellulose (HEC) as composite foam stabilizer, Na2SiO3 or KOH/Na2SiO3 as single or compound activator, respectively. The formation and enhancement mechanism of geopolymer structure were discussed. The research provides a new technical way for increasing the strength and operational reliability of conventional cement foam materials prepared at room temperature.