Lithium (Li) metal is one of the most promising anode for rechargeable batteries. However, Li dendrite growth during plating/stripping process leads to many subsequent damages, such as low Coulombic efficiency, large volume change and short circuit, which can inhibit its practical application. To suppress Li dendrite, great efforts have been focused on the current collector of Li metal battery. Herein, a facile method utilizing diffusion couples Cu-X and kirkendall effect is developed to obtain 3D porous Cu current collector for Li metal anodes. The 3D current collector has interconnected pores throughout the Cu foil, which can reduce current density, provide “cages” for dendrite and enhance structural stability. As a result, Li dendrite growth is largely suppressed, giving rise to the improvement in electrochemical performances: high Coulombic efficiency even after 200 cycles, long life span of more than 2000 h, good cycling performance in full cells, etc. Moreover, the diffusion method overcome the energy/time-comsuming disadvantages of other methods for preparing porous current collectors, so it can be generalized to other synthesis of porous metal foils as a easy, sustainable and universal method. The 3D porous current collector will promote the commercialization of high-energy Li metal batteries.