Discharge of mine water has drawn increasing concern due to its contribution to elevated river salinity and soil salinization. Understanding the evolution of cations in mine water is crucial for developing efficient treatment technologies. This study investigated the release patterns of major cations from coal and gangue collected from the Pingdingshan mining area under various conditions, including particle size and solution chemistry. The underlying mechanisms controlling the mineralization characteristics of mine water were elucidated. The results showed that the particle size of coal and gangue significantly influenced ion release and solution pH. A smaller particle size enhanced the dissolution of aluminosilicates and carbonates in the coal-bearing strata, leading to increased release of primary ions such as Si and Al. Gangue was the primary source of Si and Al ions, while coal predominantly contributed Ca ions; furthermore, the presence of gangue suppressed the release of Ca ions. The ion release patterns in actual mine water differed from those in deionized water, with Ca and Mg concentrations in mine water being mainly governed by coal. The study demonstrates that the synergistic interaction between coal and gangue significantly impacts the chemical properties of mine water, while the initial solution environment primarily regulates the dynamic processes of ion release and pH changes. By systematically revealing the evolution of major cations under different particle sizes, this research clarifies the chemical behavior of coal and gangue within the mine water system and its influence on water quality, providing valuable insights for reducing treatment costs and developing innovative technologies for managing highly mineralized mine water.