Selective laser sintering (SLS), known as one of the powder-based Additive Manufacturing technologies developed in 1980s, has unique advantages in building porous ceramics with high geometry complexity. This accomplished study provides a strategy to prepare mullite foams with controlled pore structures and low thermal conductivity by SLS using fly ash hollow sphere (FAHS) as raw materials. The major superiority of using FAHSs as raw materials to prepare ceramic foams can be listed as follow:(i) their particle size and distribution can be well adjusted before use, which can control the pore size and porosity of ceramic objects; (ii) their shell walls can act as skeletons, which might potentially improve mechanical properties of mullite foams;(iii) they are ultra-low cost, and the recycling of such solid waste can help solve pollution problem caused by FAHSs.The subject has a considerable practical interest because SLS is an emerging technology for manufacturing complex-shaped porous ceramic objects with great added value, and it also brings new sights into the advanced utilization of FAHS solid waste.