Abstract: Large size (cylinder diameter was larger than 140 mm) porous copper with long cylindrical pores was prepared by metal-gas eutectic directional solidification method under the mixture gas of hydrogen and argon. Gasarite copper with different porosities was obtained under different pressures. The effect of pressure on porosity was investigated. The results show that when the argon partial pressure was constant and small, the porosity decreased with the increase of hydrogen partial pressure, while increased when the pressure was constant and large. When the hydrogen partial pressure was constant, the porosity decreased with the increase of argon partial pressure.