Abstract: In recent years, with the increase of environmental protection requirements and the implementation of the "dual carbon target", the proportion of coal in China’s energy consumption is gradually decreasing year by year. Nevertheless, its consumption is still increasing annually and remains the main raw material of energy in China. The combustion of coal generates a large amount of fly ash, which, if not properly disposed of and treated, can be carried by the wind into the air and subsequently settle into rivers and onto soil, causing significant damage to the environment and human health. In recent years, the production of fly ash in China has gradually increased, yet its utilization rate is relatively low compared to other countries. In 2016, China’s fly ash utilization rate was around 70%, while the EU’s (European Union’s) rate was approximately 90%, and Japan’s rate was nearly 100%. Therefore, it is imperative to increase the utilization rate of fly ash. Given that fly ash is rich in silicon and aluminum, which are similar to the chemical components required for the production of molecular sieves, there are considerable prospects for utilizing fly ash to produce molecular sieves. The composition of fly ash is complex, and some crystalline silicon and aluminum compounds in fly ash exhibit high stability. Prior to the preparation of molecular sieves, activation treatment is required to convert them into silicates and aluminates with activity suitable for molecular sieve preparation. Subsequently, through synthesis processes including aging, crystallization, washing, and drying, the silicates and aluminates are converted into molecular sieves. Different experimental conditions can yield different types of molecular sieves. In order to understand the current status of molecular sieve preparation from fly ash, common activation methods of fly ash are reviewed, including mechanical activation, hydrothermal activation and high-temperature activation. It also systematically discusses the synthesis methods of molecular sieves, encompassing hydrothermal synthesis, microwave-assisted synthesis, alkali fusion, seeding, and transforming crystal types. Among these, hydrothermal synthesis and alkali fusion are the most commonly used, while seeding is still in the research stage and holds certain development prospects. Common types of fly ash molecular sieves include types A, P, X, Y, and ZSM‒5. Generally, their preparation is based on hydrothermal synthesis, with ultrasonic, microwave, and alkali fusion methods serving as auxiliaries to enhance conversion rates and product purity. Finally, the applications of molecular sieves are introduced. The primary applications include: treating pollutants in wastewater, such as metal ions like Ni²⁺; adsorbing harmful gases such as CO₂, NO₂, and VOCs due to their large specific surface area; reducing the toxicity of contaminated soil or immobilizing metals in the soil with low density, large pores, and moderate particle size; serving as catalysts or catalyst supports. The preparation of fly ash into molecular sieves is in line with the concept of sustainable development, but there are still some technical difficulties in this field. Future research will focus on improving the conversion rate and crystallinity of fly ash molecular sieves, as well as their applications in catalysis and environmental protection.