Abstract: Sialon ecomaterials with different compositions were synthesized by a carbothermal reduction-nitridation process with fly ash and carbon black as raw materials. Effect of synthesis temperature on the phase composition was investigated. The microstructure was observed by SEM. The carbothermal reduction-nitridation process of fly ash was also analyzed. The results indicated that synthesis temperature has a remarkable effect on the phase composition of the materials. Increasing synthesis temperature accelerates the decomposition of mullite and the formation of Sialon. The Sialon materials with different compositions can be synthesized by controlling the temperature. The (O'+β)-Sialon/mullite, (X+β)-Sialon/corundum and β-Sialon materials can be synthesized at 1350~1400°C, 1450~1500°C and 1550°C for 6 h, respectively. The average particle size of β-Sialon synthesized at 1550°C is around 2~3 μm. The carbothermal reduction-nitridation process of fly ash consists of the nitridation formation process of O'-Sialon, X-Sialon and β-Sialon, and the conversion processes of O'-Sialon to X-Sialon and β-Sialon as well as X-Sialon to β-Sialon.