To strengthen the formation of Hydroxyl radical (HO center dot) on anode, pressurized water electrolysis under constant temperature were carried out in this work. The HO center dot formation was verified by electrochemistry-electron spin resonance (ESR) and bauxite desulfurization in the same pressurized reactor with different cell designs. With increasing pressure, the current density was increased. However, the equilibrium potential of anode and the initial potential of oxygen evolution reaction (OER) were negative shifted with increasing pressure. Results revealed that pressure promoted the early steps of OER but inhibited subsequent transformation. The apparent transfer coefficient of the anode (b(a) and b(c)) further proved that the pressure play a positive role on the OER reserve reaction and promoted the formation of HO center dot. R-ct and R-s were all decreased with increasing pressure, demonstrating that pressure improved the mass transfer and reaction of the OER. The electrolysis desulfurization and ESR experiments have clearly supported the positive role of pressure on strengthening the HO center dot formation. From electrolysis with 0.1 MPa, HO center dot signal was detected by ESR when constant potential was 0.8 V on anode, while the signal arose at 0.7 V under 1.0MPa, indicating that HO center dot was formed in advance under pressure. (C) 2019 Elsevier Ltd. All rights reserved.