In this study, pyrite samples from the Yankan Coal Mine near the Shandi River in Yangquan City were studied in an oxidation dissolution experiment. Pyrite was studied at different solid-liquid ratios (1:100, 1:50, and 1:20), and the oxygen concentration used was equal to the value in the ambient environment, about 20.95% of the air volume. The pH, oxidation-reduction potential (Eh), and soluble salt concentration (EC), total iron concentration, and SO42− concentration in the solution at different reaction times were measured with respect to time. The oxidation reaction rate of pyrite was calculated using the SO42− concentration and the factors influencing the oxidation rate at different conditions were discussed. The experimental results showed that, after pyrite was oxidized and dissolved at solid-liquid ratios of 1:20, pyrite decrease from acid generation of the SO42−formation, then the pH of the solution increased, at solid-liquid ratios of 1:100, 1:50, and 1:20, the overall Eh and EC values decreased. No matter what solid-liquid ratio is adopted for the reaction, the Fe2+ concentration is higher than Fe3+ concentration, and the Fe2+ and total iron concentration all increase with the increase of solid-liquid ratio, while Fe3+ gradually increases, reaching a trend of relatively stable and slowly decreasing. The average apparent release rate of Fe was proportional to the different solid-liquid ratios. The oxidation reaction rate of pyrite under acidic conditions was directly related to the concentration of reactants, and a faster oxidation rate was observed at higher concentrations due to the larger reaction contact area.