The invention which provides waste brick tile / straw foam concrete and a preparation method thereof relates to a lightweight building material. The foam concrete is a porous material obtained by mixing more than 90% of a main material comprising industrial and agricultural wastes of waste brick tiles, slag, straws and the like, an additive, a foaming agent and water according to a ratio, stirring,cast-molding and maintaining. The foam concrete which has the functions of light weight, low heat conduction coefficient, heat insulation, sound insulation and fire resistance, water resistance, freezing resistance, cracking resistance, shock resistance and the like and has the advantages of low production cost, simple manufacturing process, realization of onsite casting of prefabricated products, use convenience and safety, changing of wastes into valuables, reaching of energy-saving low-carbon effects, reduction of pollution of the wastes to the environment, ecological environment protection, and nation and civilian benefiting, contributes to the creation of the saving and low carbon society in China.