Abstract: The effect of relative density on the compressive properties of TC4 body-centered cubic（BCC） lattice structure fabricated by selective laser melting was studied by quasi-static compression test. The deformation behavior and failure mode of TC4 BCC lattice structure with different relative densities were analyzed by combining test and finite element analysis. The results show that the change of relative density does not affect the equivalent stress concentration position of lattice structure during the process of compression deformation, so it shows shear failure. The increase of relative density increases the compressive strength and energy absorption capacity of the lattice structure, but the energy absorption efficiency decreases.The compressive strength and energy absorption capacity of the sample with relative density of 70% are strongest, which are543 MPa and 63.0 MJ·m³, respectively, but the energy absorption efficiency is only 65.2%, which is far less than 116.6% of the sample with relative density of 30%. The fracture mechanism of all the samples is ductile-brittle mixed fracture.