In this paper, based on the D-TPMS lattice structures, two types of TPMS lattice structure models of homogeneous and variable density are designed by the regulation method of linear gradient wall thickness, and prepared by selective laser melting technology. The effects of relative density, printing direction and model type on the mechanical properties and energy absorption characteristics are analysed experimentally, and the stress distribution and damage mechanism of the variable-density lattice structures are verified by the finite element method. The results show that the damage of the homogeneous TPMS lattice structure is 45o shear fracture, which occurs at the early stage of plastic deformation; the damage of the variable density TPMS lattice structure is interlayer collapse, and the overall structure has excellent load bearing and energy absorption capacity. When the relative density of the TPMS lattice structure is 0.275, the ultimate compressive strength of the homogeneous TPMS lattice structure is up to 193.8 MPa, the deformation amount is 7.7%, and the cumulative value of energy absorption is 11.76 MJ/m3, whereas the ultimate compressive strength of the variable-density TPMS lattice structure is up to 221.4 MPa, and the structure is still intact when the deformation amount is 50%, and the cumulative value of energy absorption is up to 77.52 MJ/m3, and the ultimate compressive strength of the TPMS lattice structure is up to 3.5 MJ/m3. The cumulative energy absorption value can reach 77.52 MJ/m3, which is 6.59 times higher than that of the homogeneous structure, indicating that the variable-density TPMS lattice structure has good energy absorption effect and excellent load-bearing performance, and it has a large application prospect in the field of collision avoidance and energy absorption.