In the present work, the low-load uniaxial and biaxial tensile testers were employed to carry out the uniaxial and biaxial tensions systemically for porous metal bodies at different uniaxial and biaxial tensile rates. The uniaxial tensile failure mechanism is analyzed, and the results show that the macroscopical failure behavior of the foam metals with open cells differ from either the transverse rupture by maximum tensile stress criterion, or the plastic flow failure by maximum shearing stress criterion, but behaves a complicated failure mode between these two criterions. In addition, the percentage elongation after fracture results mainly from the plastic deflexion of metallic struts within the three-dimensional reticulated structure, hardly from the plastic deformation of the metallic body under uniaxial tension. From the fracture morphologies under biaxial tension, it is found that the distribution of the stress field in the cruciform specimens of the foamed metal under biaxial equal-speed tension is similar to that under biaxial unequal-speed tension, and the maximum stress line of the stress field presents the four-fold symmetric curved-side tetragon.