Body-centered-cubic porous structures of Ti6Al4V titanium alloys are prepared by the selective laser melting (SLM) technology. The effects of the linear laser energy density and the microrod diameter on the compressive property along the forming direction (Z axis) and non-forming direction (X/Y axis) of these body-centered-cubic porous structures are studied. The results show that the body-centered-cubic porous structures fabricated by the SLM technology exhibit an obvious anisotropy. With the decrease of the linear energy density, the compressive strength of these body-centered-cubic porous structures increases first and then decreases. The degree of anisotropy is the lowest under the optimal parameters. With the decrease of the microrod diameter, the degree of anisotropy gradually weakens and when the microrod diameter reaches 0.4 mm, the degree of anisotropy is only about 3%. The research indicates that, even an isotropic porous structure, after fabrication by SLM technology, shows an obvious anisotropy. Such an anisotropy is related to the forming quality and the interlayer boundary which can be weakened to a certain extent by adjusting process parameters and changing model characteristic dimensions.