A novel technique of flyash utilization was presented and mullite ceramics were prepared from flyash and desilication-flyash. The effect of desilication process was analyzed and the result shows that the only difference between flyash and desilication-flyash lies in the silica content, which is caused by the removal of silicate glassy phase during the desilication process. The physical and mechanical properties of flyash sample and desilication-flyash samples were measured. All results indicate that the desilication-flyash is more suitable to be used to prepare the mullite ceramics than flyash. The inner structure of flyash particle was first discovered, which can help us form a new description of the flyash particle and finally benefit the utilization of flyash. Lath-like mullite crystals appeared in high-iron samples and needle-like mullite crystals were observed in low-iron samples. The flexural strength of high-iron sample was higher than that of low-iron sample because of the formation of network structure consisting of many interlocked lath-like mullite crystals in high-iron samples. (C) 2010 Elsevier Ltd. All rights reserved.