Open circuit potential, potentiodynamic polarization plots and electrochemical impedance spectroscopy for pyrite in 0.1 M sulfuric acid in the temperature range of 200 to 350 C-o and pressure range of 25 to 40 MPa were measured, with the aid of a self-designed electrochemical measurement set-up which can operate at high temperature and high pressure. Results show that increased temperatures benefit the oxidation of pyrite: at 40 MPa, when the temperature was rised from 200 to 350 C-o, corrosion potential (E-corr) decreased from - 199.83 to - 778.78 mV, corrosion current density (i(corr)) increased from 4.33 to 22.16 mA/ cm(2), polarization resistance (R-p) decreases from 34.11 to 3.85 Omega center dot cm(2), resistance of the passive layer (R(p)l) decreased from 42.16 to 2.48 Omega center dot cm(2). Effects of pressure were also considered, at 300 C-o, when pressure was increased from 25 to 40 MPa, Ecorr decreased from -621.48 to -713.25 mV, however, i(corr) and R-p rarely changed.