A new developed technology for extracting alumina from coal fly ash was studied in this paper. In this technology, coal fly ash is first sintered with ammonium sulfate, forming ammonium aluminum sulfate in the resultant product, where alumina can be easily leached without using any strong acid or alkali. The products obtained under different sintering conditions were characterized by X-ray diffractometry. Alumina extraction efficiency of these products was also investigated. The results show that the sintering temperature and time substantially influence the phase composition and alumina extraction efficiency of sintered products, while the heating rate has little influence. The optimal sintering condition is 400 degrees C for 3 h in air with a heating rate of 6 degrees C.min(-1). Under the optimal sintering condition, the alumina extraction efficiency from as-sintered coal fly ash can reach 85% or more. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.