The geothermometer is usually used to calculate the deep temperatures of geothermal reservoirs in the geothermal system,but if the chemistry component is not balanceable in the geothermal reserviors,the equilibrium temperature of the deep reservior estimated by the geothermometer is not true.Taking thermal groundwater of the eighth coal mine in Pingdingshan for example,both the Na-K-Ca diagram and the lg(Q/K) figure are employed to exam the mineral-fluid equilibrium state qualitatively and quantificationally,which may lay a theoretical foundation for the choice and application of geothermometers.