With the increase in global warming, building energy saving becomes a principal policy for most countries. About 70% of the energy consumption loss of buildings is through the external walls of the buildings. Ultra-lightweight foam concretes with dry density of 150-300 kg · m-3 as the thermal insulation materials have been commercially prepared and used in building insulation engineering in China. This paper reports the raw materials and procedures for preparation of ultralightweight foam concretes by chemical foaming (UFC-C) and physical foaming (UFC-P). The characteristics of the air-voids structure, the mechanical properties, the water absorption, the thermal conductivity and the fire resistance of UFC-C and UFC-P were summarized in this paper. Based on existing research progress, the future research works were presented.