The invention relates to a method for preparing a lightweight 
mullite refractory by high-
alumina fly ash and relates to the technical fields of 
solid waste comprehensive utilization and refractories. According to the method, waste from a power 
plant, namely high-
alumina fly ash, is used as a 
raw material; commercial 
alumina is added according to the composition design; the mixture is fired and crushed to prepare lightweight 
mullite aggregate and lightweight 
fine powder, with different granularities; then 
silicon dioxide 
fine powder is additionally added; 
polystyrene spheres or 
sawdust is used as a pore-forming agent, 
aluminate cement is used as a gelling agent, and 
sodium hexametaphosphate is used as a 
water reducer; the lightweight 
mullite refractory is prepared through the processes such as forming by vibration pouring, curing, 
drying and 
sintering. The main high-temperature-resistant phase of the lightweight 
refractory is mullite phase and 
corundum phase; the lightweight mullite refractory comprises the main 
chemical constituents: 55.0-70.0 wt% of Al2O3, 25.0-40.0 wt% of SiO2 and 0-5.0 wt% of other impurities. Compared with the prior art, the method has the characteristics of wide 
raw material source, low production cost, low 
energy consumption, high mullite content, high performance, long service life, and simple operation in the preparation process; significant economic and environmental benefits can be generated.