Carbonate minerals and water (or geofluids) reactions are important for modeling of geochemical processes and have received considerable attention over the past decades. The calcite dissolution rates from 50°C to 250°C at 10 MPa in deionized water with a flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor. The dissolution began near the equilibrium with c/ceq > 0.3 and finally reached the equilibrium at 100°C-250°C, so the corresponding solubility was also determined as 1.87, 2.02, 2.02 and 1.88′10-4·mol/L at 100°C, 150°C, 200°C and 250°C respectively, which was first increasing and then switching to decreasing with temperature and the maximum value might occur between 150°C and 200°C. The experimental dissolution rate not only increased with temperature, but also had a rapid increase between 150°C and 200°C at a constant flow rate of 4 mL/min. The measured dissolution rates can be described using rate equations of R = k(1-c/ceq)n or R = kc-n. In these equations the reaction order n changed with temperature, which indicates that n was a variable rather than a constant, and the activation energy was 13.4 kJ/mol calculated with R = k(1-c/ceq)n or 18.0 kJ/mol with R = kc-n, which is a little lower than the surface controlled values. The varied reaction order and lower activation energy indicates that calcite dissolution in this study is a complex interplay of diffusion controlled and surface controlled processes.