A fermented brown coal residue soil conditioner is prepared by evenly mixing brown coal residues, brown coal essence liquid, medical stone, composite bone meal, dry sapropel, and a composite microorganism inoculant according to a certain weight ratio and then fermenting the mixture. The absorbing performance and salt-base exchange performance of the soil conditioner are strong, the soil conditioner can improve the soil breathability, the crop respiratory effect is improved, the absorbing performance of roots is enhanced, the lateral root growth is promoted, the crop photosynthetic effect is effectively improved, the nutrients for plants are balanced, and the growth is promoted. The wastes (brown coal residues and brown coal essence liquid), which are generated during the brown coal processing process, are utilized, the wastes are converted into valuable resources, the product addition value is increased, an income increasing method is developed for humic acid producing entrepreneurs, a novel thinking is provided for developing soil conditioner, and the soil conditioner eventually improves the soil quality and increases the economic profits.