A method for producing lightweight and high-strength ceramsite from coal fly ash was presented. It provides a potential solution to the problem of coal fly ash stockpiling and makes effective use of SiO₂, Al₂O₃ and other substances. Based on the thermodynamic analysis, an optimized method for the preparation of lightweight high-strength ceramsite by sintering at high coal fly ash doping (60%-90%, mass fraction) was designed. The mineral transformation in the complex silicate systems was studied. The cooling method, the roasting process and the raw material formula were improved. At the roasting temperature of 1200 ℃ and the holding time of 5 min, the density of the ceramsite produced was less than 0.93 g/cm³ and the strength was as high as 1.08 kN. The specific strength of ceramsite produced by this approach was significantly higher than that of several randomly purchased ceramsite products in the market.