Pressure effect on the phase transformation process of the ε-phase of splat quenching Pe-C-Sb alloy has been investigated by using X-ray powder photography. The experimental results show that high pressure will not only increase the stability of the ε-phase remarkably but also change its phase transformation process. At 4.7 GPa, as the temperature of stability of ε-phase increases to 450℃, a new metastable phase of orthorhombic structure, being absent at normal pressure, will appear. By raising annealing temperature to 560℃, the orthorhombic metastable phase begins to transform into Fe3C which will decompose into carbon (graphite) and γ-Fe on further increasing annealing temperature to 800℃. At this time, the alloy is composed of C (graphite), γ-Fe, Sb and another unknown phase.