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The melting curves of iron over a wide range of pressures were determined by the molecular dynamics (MD) simulations with the Sutton-Chen version of EAM (embedded atom method). The melting of iron was simulated with two methods, that is, the hysteresis (one-phase) approach and the two-phase approach. Both methods strongly reduced the overheating, and their results are in the close proximity at the applied pressures. The obtained melting curves are consistent with both the diamond anvil cell (DAC) experiments at ambient pressure and the shock wave (SW) measurements at high pressure. During the investigation of the atomic structures of iron, we found a slight increase in the coordination number on melting. When taking account of the ultrapressure melting curves obtained by the Clausius-Clapeyron slope, we found that the starting point is the key to determine the melting curves, and the melting temperatures computed by the Clausius-Clapeyron slope might change dramatically if the initial temperatures change. Finally, the thermal equation of state (EOS) and the pressure dependence of entropy of fusion AS of iron have also been obtained.