Acid sulfate soil is soil that can be used for agriculture. Problems that are often encountered in acid sulfate soils are high acidity due to pyrite, low soil pH, and high levels of nutrient elements such as aluminum and iron which cause them to be toxic to plants. To overcome this problem, it can be done by adding ameliorant materials such as fly ash. coal. The aim of this research is to determine the effect of the best dose of coal fly ash on dissolved Al-dd and Fe in acid sulfate soil. The experimental land was taken in the rice fields of Jejangkit Muara Village, Jejangkit District, Barito Kuala Regency, South Kalimantan. The incubation treatment was carried out in the greenhouse of the soil department of the Faculty of Agriculture and the analysis was carried out in the Soil Chemistry-Physics Laboratory, Faculty of Agriculture, Lambung Mangkurat University. The research will begin in July 2024. The results showed that treatment with a dose of 150 Mg ha-1 gave the best results on soil pH (7.31), soluble P (16.07 ppm P), N-minerals (7.35 mg kg-1). The research results show that the application of coal fly ash can reduce Al-dd and Soluble Fe content.