In order to enhance the comprehensive utilisation rate of mine water and alleviate the problem of high cost of mine water treatment and purification, this paper is predicated on the concept of an ‘underground water reservoir’, focusing our research on the purification and adsorption effects of collapsed coal rock accumulations in goaf areas on mine water. Three groups of coal particles with varying particle sizes were selected for use in the filtration device. The suspended mine water, containing different concentrations of gangue powder, was imported for analysis. This was conducted in order to evaluate the impact of collapsed coal rock piles on the suspended matter of the mine water, under conditions of different filling particle sizes, flow rates, times and circulation distances. The results show: it was determined that the filler with a smaller particle size exhibited a superior adsorption effect on the suspended matter in mine water. Additionally, the lower flow rate, longer transport distance and prolonged filtration period were observed to have a more pronounced adsorption effect on the suspended matter. On the basis of theoretical research, 15102 workface of Shanxi Lingzhida Coal Mine was selected as the object of engineering practice. It was found that the collapsed coal rock accumulations in the mining area had a beneficial filtration and purification effect on mine water. The results can provide a good theoretical basis for underground treatment of mine water and serve as an engineering demonstration.