As a high-efficient heat transfer device via phase-change of the working fluid, heat pipes are widely used in aerospace, thermal control system, and electronic heat dissipation. The wick inside the pipe provides the capillary for the circulating flow of the working medium in the pipe, and it is a core part of the heat pipe. Therefore, developing a new wick type with multi-scale structures, low contact thermal resistance, and high heat transfer performance is significant. Previously, porous copper surfaces have been proven to enhance boiling heat transfer performance significantly, but how it works in a two-phase loop thermosyphon is still unknown. Here, the method of in-tube flow electrochemical deposition was adopted to deposit porous copper inside the cylindrical evaporator of the two-phase closed-loop thermosyphon. Wicking test experiments show that the porous copper samples all exhibit super-hydrophilic properties. Among them, the porous copper sample (S-1.5M) with a H₂SO₄ concentration of 1.5M has the best capillary force. Then, the S-1.5M sample was used as the evaporator for a thermosiphon. Its heat transfer performance was tested and compared with a thermosyphon with a smooth copper surface as the evaporator. The results show that the porous copper sample was much easier to start up than the smooth copper sample. Compared with the smooth surface evaporator, the porous copper evaporator can effectively improve the heat transfer performance of the two-phase closed-loop thermosyphon. The loop thermo-syphon with porous copper evaporator is much easier to start-up than that with smooth evaporator. The loop thermo-syphon with porous copper evaporator can also start up in a lower power compared to that with smooth evaporator. Under the same power, the bottom plate temperature of the porous copper evaporator is significantly lower than the smooth surface evaporator. When the input power is 350W, the bottom plate temperature of S-1.5M was about 6 °C lower than that of the smooth surface evaporator. At that time, the total thermal resistance of the porous sample is about 0.165 °C/W, which is about 10% decrease compared to smooth sample. The reason is that the porous copper sample has a rich micro-nano structure, which provides more vaporized cores and effectively reduces the wall superheat.